test: re-enable issue4348.go.

The test array is too large to fit a stack frame
but can be a global.

R=golang-dev, minux.ma
CC=golang-dev
https://codereview.appspot.com/7127059
runtime: try to determine the actual type during garbage collection

If the scanned block has no typeinfo the garbage collector will attempt
to get the actual type of the block.

R=golang-dev, bradfitz, rsc
CC=golang-dev
https://codereview.appspot.com/7093045

Committer: Russ Cox <rsc@golang.org>
spec: clarify lhs syntax for range and select

Fixes issue 4653.

R=rsc, r, iant, ken, thakis
CC=golang-dev
https://codereview.appspot.com/7135058