runtime: increase stack limit in a test
Otherwise the test is flaky.
Fixes issue 4698.

R=golang-dev, iant
CC=golang-dev
https://codereview.appspot.com/7133071
go/types: add String() method to Type interface.

All implementations delegate to typeString.

Though I don't wish to exploit gri's absence to change
his code, this change is pretty low-risk and he assented to it
in the blue ink in the doc below [gophers only].
https://docs.google.com/a/google.com/document/d/1-DQ4fxlMDs9cYtnkKhAAehX6MArjOQyJsRXp-6kiJLA/edit#

R=iant, gri, gri
CC=golang-dev
https://codereview.appspot.com/7200046
go/types: expose types.IsIdentical, the Type equivalence relation.

This function is absolutely critical for clients such as
exp/ssa, and too complex for clients to duplicate.

As with CL 7200046, gri expressed in the doc below [gophers
only] before going on leave that he intended to expose such a
predicate, though his wording suggests as an interface method
of Type rather than a standalone function.  (My preference is
for binary methods to be standalone; see "On Binary Methods",
Kim Bruce, 1995).  In any case if he wishes to move it that's
easily accommodated by clients.

https://docs.google.com/a/google.com/document/d/1-DQ4fxlMDs9cYtnkKhAAehX6MArjOQyJsRXp-6kiJLA/edit#heading=h.k3bwja7xony9

R=iant, gri, iant
CC=golang-dev
https://codereview.appspot.com/7203051
doc: add mention of the Go+ community

R=golang-dev, iant, kamil.kisiel, minux.ma
CC=golang-dev
https://codereview.appspot.com/7203049
exp/ssa: API and documentation.

R=gri, iant, crawshaw, bradfitz, gri, iant
CC=golang-dev
https://codereview.appspot.com/7071058
misc/dashboard/builder: synchronize accesses to goroot, always -commit

This prevents the occasional issue when Mercurial screws up the locking
itself, and by moving the locking into this process we can use the
goroot for other things (such as automatically updating the builder
binary).

It also asks all builders to poll for new commits.

R=bradfitz, dave, minux.ma, rsc
CC=golang-dev
https://codereview.appspot.com/7178046