Produce a user message in case of stack overflow.
Change VG_(extend_stack) and VG_(am_extend_into_adjacent_reservation_client)
accordingly. 
Remove some redundant checking.
Add testcase.


git-svn-id: svn://svn.valgrind.org/valgrind/trunk@14974 a5019735-40e9-0310-863c-91ae7b9d1cf9
19 files changed