Fix 341539 VG_(describe_addr) should not describe address as belonging to client
        segment if it is past the heap end

Describes specifically an address that is in the brk data segment
or in the 'reduced' (after brk reduction) section of the brk data segment.

Based on a patch from Ivo Raisr.



git-svn-id: svn://svn.valgrind.org/valgrind/trunk@14833 a5019735-40e9-0310-863c-91ae7b9d1cf9