ReleaseNotes: Add Hexagon Target section

And mention removal of hexagonv2 and hexagonv3 support (r176859).


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@176860 91177308-0d34-0410-b5e6-96231b3b80d8
In r169695, the address space limit for tests was replaced with a data
segment limit. Now, as a complement, add a stack space limit.

Otherwise, tests may grow undesirable large at inifinite
recursion. (Seen at r176838,
test/Assembler/2010-02-05-FunctionLocalMetadataBecomesNull.ll)

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@176862 91177308-0d34-0410-b5e6-96231b3b80d8