Merge from the trunk, a bunch of changes to fix ELF segment mapping

Merge from the trunk, a bunch of changes to fix ELF segment mapping
and bias computation problems:

9020  Improve detection of where ELF sections have been mapped
9021  Don't assume that all global variables are in the data section
9022  Removed unused round_Addr_upwards function.
9024  Handle the rodata and sbss sections
9025  Accept zero size text segments.
9026  Don't worry about an unmapped, zero sized, bss segment.
9053  Fix aix5 build breakage following r9021.

git-svn-id: svn://svn.valgrind.org/valgrind/branches/VALGRIND_3_4_BRANCH@9067