Fixes #1204.

R=golang-dev, brainman, Joe Poirier, alex.brainman, adg
CC=golang-dev, math-nuts
https://golang.org/cl/2532041

R=r, r2
CC=golang-dev
https://golang.org/cl/2543044

R=adg
CC=golang-dev
https://golang.org/cl/2486043

R=rsc, r2, r
CC=golang-dev
https://golang.org/cl/2550041

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