This patch by Chris Manghane passes type information to
compiler-generated heap allocations in gccgo.  This gives us precise
type information for much of the gccgo heap, and means that garbage
collection is much more precise and less prone to errors due to
mistaking integer or float values as pointers.  Bootstrapped and ran
Go testsuite on x86_64-unknown-linux-gnu.  Committed to mainline.

Ian