R=ken
OCL=32421
CL=32421

single frame and non-overlapping variables reuse frame slots.
As a result, entering and exiting blocks no longer requires
code execution, which means jumps across block boundaries
should be doable now.  Frame slot initialization happens at
definition time now, instead of at frame creation time.  As an
added bonus, Scope's are now exclusively compile-time objects
and we no longer need to specially track the function
activation frame for access to out vars.

R=rsc
APPROVED=rsc
DELTA=313  (102 added, 90 deleted, 121 changed)
OCL=32416
CL=32420

R=ken
OCL=32419
CL=32419

R=r
DELTA=9  (8 added, 0 deleted, 1 changed)
OCL=32413
CL=32418

so that == on func means that the
functions originated in the same
execution of a func literal or definition.

before, there was an inconsistency:

	func() {x++} != func() {x++}

but

	func() {} == func() {}

this CL makes the second case != too,
just like

	make(map[int]int) != make(map[int]int)

R=r
DELTA=202  (71 added, 62 deleted, 69 changed)
OCL=32393
CL=32398

This makes the list closed under its provided operations.

R=rsc,gri
APPROVED=rsc
DELTA=18  (14 added, 0 deleted, 4 changed)
OCL=32388
CL=32395

R=rsc
DELTA=3  (3 added, 0 deleted, 0 changed)
OCL=32389
CL=32392

easier and faster to read.  they are now either a one-byte value or a n-byte value
preceded by a byte holding -n.

R=rsc
DELTA=150  (45 added, 7 deleted, 98 changed)
OCL=32381
CL=32387

R=ken
OCL=32264
CL=32386

(reported by iant)

R=r
DELTA=50  (32 added, 12 deleted, 6 changed)
OCL=32263
CL=32385

R=rsc
APPROVED=rsc
DELTA=304  (281 added, 0 deleted, 23 changed)
OCL=32361
CL=32382

gofmt formatted source code looks pretty good already;
with a bit more fine-tuning it should be great.

printer.go:
- Implemented comment intersperse algorithm.
  The approach is a result of many trial-and-error
  experiments but at this point reasonably simple
  and open to arbitrary fine-tuning.

parser.go:
- Simplified handling of lead and line comments
  (formerly called leading and trailing comments).
- Use a comments list instead of an array (I may
  change this back - this is not obviously better
  and uses more space).

doc.go:
- Remove comments from AST nodes that have been
  'consumed' in the documentation to avoid duplicate
  printing of them. Allows for better control of
  what is printed w/o use of printing control flags
  (which are hard to use and not fine-grained enough).

Corresponding adjustments to various clients of these
files.

R=rsc
DELTA=478  (275 added, 108 deleted, 95 changed)
OCL=32185
CL=32380

jump to the post statement instead of the condition check.

R=rsc
APPROVED=rsc
DELTA=10  (6 added, 1 deleted, 3 changed)
OCL=32359
CL=32379

TBR=rsc
OCL=32330
CL=32330

- Provides analogous functionality to a doubly-linked list
  implementation.
- Completely symmetric set of operations.
- Operations on the ADT do not lead to results that are
  outside the domain of the ADT (closed interface).
- Alternative to container/list.

R=rsc
DELTA=489  (489 added, 0 deleted, 0 changed)
OCL=32284
CL=32323

R=r
DELTA=13  (8 added, 2 deleted, 3 changed)
OCL=32291
CL=32322

pow10 was giving up too easily.

R=r
DELTA=4  (0 added, 3 deleted, 1 changed)
OCL=32310
CL=32321

and decrement.  blockCompilers now form a tree the mimics the
nesting of scopes and provide convenient ways to enter and
exit scopes.  blockCompilers also track the break and continue
PC for the current block.  The statement testing interface now
works in lists of statements, which simplifies a bunch of
things.

R=rsc
APPROVED=rsc
DELTA=401  (335 added, 44 deleted, 22 changed)
OCL=32308
CL=32317

- derive int, uint, float, uintptr decoders based on their size
- add overflow checks in decode

R=rsc
DELTA=407  (281 added, 44 deleted, 82 changed)
OCL=32286
CL=32290

R=rsc
DELTA=16  (16 added, 0 deleted, 0 changed)
OCL=32288
CL=32288

R=rsc
DELTA=5  (5 added, 0 deleted, 0 changed)
OCL=32283
CL=32287

R=r,gri,rsc
APPROVED=rsc
DELTA=53  (12 added, 6 deleted, 35 changed)
OCL=31822
CL=32282

pointer to the Type instead of the address of the Type.

R=rsc
APPROVED=rsc
DELTA=1  (0 added, 0 deleted, 1 changed)
OCL=32265
CL=32279

R=ken
OCL=32261
CL=32261

unpacking for assignments, call arguments, and returns.  This
change revamps the whole assignment compilation system to be
multi-valued, using the new MultiType type and multiV value.
Function calls, returns, and assignments now share a lot of
code and produce very consistent error messages.

R=rsc
APPROVED=rsc
DELTA=510  (335 added, 74 deleted, 101 changed)
OCL=32248
CL=32258

R=ken
OCL=32257
CL=32257

R=rsc
DELTA=160  (124 added, 0 deleted, 36 changed)
OCL=32233
CL=32256

R=ken
OCL=32255
CL=32255

R=ken
OCL=32253
CL=32253

R=ken
OCL=32252
CL=32252

for slice or string x.

R=ken
OCL=32249
CL=32249

R=rsc
APPROVED=rsc
DELTA=2  (0 added, 0 deleted, 2 changed)
OCL=32245
CL=32247

R=ken
OCL=32244
CL=32244

	a := true;
	a |= a;
in the front end.

R=ken
OCL=32240
CL=32243

R=ken
OCL=32239
CL=32239

the size of chunk with uncompressed data (00 is terms of DEFLATE).

APPROVED=rsc
DELTA=15  (14 added, 0 deleted, 1 changed)
OCL=32105
CL=32238

saving of sp was too far away from use in scanstack;
the stack had changed since the sp was saved.

R=r
DELTA=9  (4 added, 2 deleted, 3 changed)
OCL=32232
CL=32237

function calling.  Implement a type compiler and named types.
Implement a universal scope containing built-in named types,
and some built-in constants.  Implement a simple virtual
machine for executing statements and single-valued return.

Fix many places that incorrectly dealt with named types.  In
particular, the Type.Zero methods now use the type's bit count
to determine the appropriate value representation.  As a
result, a bit count of 0 now means architecture-dependent and
bounded types use unsafe.Sizeof to determine the correct
bounds.  Previously, the bounds on a 32-bit machine would have
been wrong.

Eliminated Type.compatible, since the implementation is
equivalent for all types.  Added Type.rep that shallowly
strips named types.  Replaced almost all uses of Type.literal
with Type.rep.

Fix implementation of assign-op's so it only evaluates the
left side once.  As part of this, there is now a generic way
to separate out the effect and value of an expression.

R=rsc
APPROVED=rsc
DELTA=1530  (1244 added, 68 deleted, 218 changed)
OCL=32184
CL=32230

TBR=r
OCL=32225
CL=32225

R=rsc
DELTA=298  (202 added, 0 deleted, 96 changed)
OCL=32006
CL=32224