Fixes #1151.

R=rsc
CC=golang-dev
https://golang.org/cl/2469043

Adds func (z *Int) RandIntn(src rand.Source,n *Int) *Int

R=rsc
CC=golang-dev, gri
https://golang.org/cl/2315045

R=r, r2
CC=florian, golang-dev
https://golang.org/cl/2554042

R=ken2
CC=golang-dev
https://golang.org/cl/2473042

Missed a case, so now generalized.

R=ken2
CC=golang-dev
https://golang.org/cl/2540042

TBR=r
CC=golang-dev
https://golang.org/cl/2556041

No multiple processes/locks, managed to compile
and run a hello.go (with print not fmt).  Also test/sieve.go
seems to run until 439 and stops with a
'throw: all goroutines are asleep - deadlock!'
- just like runtime/tiny.

based on Russ's suggestions at:
http://groups.google.com/group/comp.os.plan9/browse_thread/thread/cfda8b82535d2d68/243777a597ec1612

Build instructions:
cd src/pkg/runtime
make clean && GOOS=plan9 make install
this will build and install the runtime.

When linking with 8l, you should pass -s to suppress symbol
generation in the a.out, otherwise the generated executable will not run.

This is runtime only, the porting of the toolchain has already
been done: http://code.google.com/p/go-plan9/source/browse
in the plan9-quanstro branch.

R=rsc
CC=golang-dev
https://golang.org/cl/2273041

R=ken2
CC=golang-dev
https://golang.org/cl/2555041

R=r, r2
CC=golang-dev
https://golang.org/cl/2506045

R=ken2
CC=golang-dev
https://golang.org/cl/2519044

R=ken2
CC=golang-dev
https://golang.org/cl/2479043

R=rsc
CC=golang-dev
https://golang.org/cl/2542042

R=rsc
CC=golang-dev
https://golang.org/cl/2543043

R=rsc, PeterGo
CC=golang-dev
https://golang.org/cl/2519043

Because the SB is only good for 8k and Go programs
tend to have much more data than that, SB doesn't
save very much.  A fmt.Printf-based hello world program
has  360 kB text segment.  Removing SB makes the text
500 bytes (0.14%) longer.

R=ken2, r2, ken3
CC=golang-dev
https://golang.org/cl/2487042

R=rsc, brainman
CC=golang-dev
https://golang.org/cl/2543042

R=ken2
CC=golang-dev
https://golang.org/cl/2481042

R=adg
CC=golang-dev
https://golang.org/cl/2521042

or at least gather more information

R=ken2
CC=golang-dev
https://golang.org/cl/2515042

R=rsc
CC=golang-dev
https://golang.org/cl/2519042

Also change the span-dependent jump algorithm
to use fewer iterations:

* resolve forward jumps at their targets (comefrom list)
* mark jumps as small or big and only do small->big
* record whether a jump failed to be encodable

These changes mean that a function with only small
jumps can be laid out in a single iteration, and the
vast majority of functions take just two iterations.
I was seeing a maximum of 5 iterations before; the
max now is 3 and there are fewer that get even that far.

R=ken2
CC=golang-dev
https://golang.org/cl/2537041

The old code said

	if(x) {
		handle a
		return
	}
	aa = *a
	rewrite aa to make x true
	recursivecall(&aa)

The new code says

	params = copy out of a
	if(!x) {
		rewrite params to make x true
	}
	handle params

but it's hard to see that in the Rietveld diffs because
it gets confused by changes in indentation.

Avoiding the recursion makes other changes easier.

R=ken2
CC=golang-dev
https://golang.org/cl/2533041

Using explicit relocations internally, we can
represent the data for a particular symbol as
an initialized block of memory instead of a
linked list of ADATA instructions.  The real
goal here is to be able to hand off some of the
relocations to the dynamic linker when interacting
with system libraries, but a pleasant side effect is
that the memory image is much more compact
than the ADATA list, so the linkers use less memory.

R=ken2
CC=golang-dev
https://golang.org/cl/2512041

R=r
CC=golang-dev
https://golang.org/cl/2526041

R=r, r2
CC=golang-dev
https://golang.org/cl/2493043

R=adg
CC=golang-dev
https://golang.org/cl/2525042

R=r
CC=golang-dev
https://golang.org/cl/2525041

R=ken2
CC=golang-dev
https://golang.org/cl/2520042

Suggested by fango (fan.howard@gmail.com)

R=r, r2
CC=golang-dev
https://golang.org/cl/2514041

Fixes #1195.

R=rsc
CC=golang-dev
https://golang.org/cl/2504043

R=ken2
CC=golang-dev
https://golang.org/cl/2471043

R=r, r2
CC=golang-dev
https://golang.org/cl/2494042

R=stephenm
CC=golang-dev
https://golang.org/cl/2471042

R=r, rsc, r2
CC=golang-dev
https://golang.org/cl/2499041

R=rsc, r
CC=golang-dev
https://golang.org/cl/2473041

R=rsc, iant, agl
CC=golang-dev
https://golang.org/cl/2052042

After a fill(), there is nothing to back up.  Make sure UnreadRune
recognizes the situation.

Fixes #1137.
(Stops the crash, but doesn't make UnreadRune usable after a Peek()).

R=rsc
CC=golang-dev
https://golang.org/cl/2498041

The remaining failures include:

* something about bit operations?
	crypto/block
	encoding/binary

* something about file I/O?
	archive/tar
	archive/zip
	debug/dwarf
	debug/elf
	debug/macho
	image/png

* floating point
	cmath
	expvar
	flag
	fmt
	gob
	json
	math
	strconv
	template
	xml

* network (maybe fixed by a pending CL)
	http
	netchan
	rpc
	rpc/jsonrpc
	syslog
	websocket

* line numbers
	log

* haven't bothered / not sure
	exp/datafmt
	exp/eval
	go/printer
	os
	os/signal
	testing/quick

R=ken2
CC=golang-dev
https://golang.org/cl/2496041

R=rsc
CC=golang-dev
https://golang.org/cl/2475042

The Plan 9 tools assume that long is 32 bits.
We converted all instances of long to int32 when
importing the code but missed the print formats.
Because int32 is always int on the compilers we use,
it is never correct to use %lux, %ld, etc.  Convert to %ux, %d, etc.

(It matters because on 64-bit gcc, long is 64 bits,
so we were printing 32-bit quantities with 64-bit formats.)

R=ken2
CC=golang-dev
https://golang.org/cl/2491041