Reduce memory needed for symbols, by having the tocptr and local_ep
(used for ppc64 platforms) #ifdef-ed and accessed by macros
that becomes NOP on non ppc64 platforms.
This decreases the debuginfo memory by about 2.5 Mb on a big 32 bit application.

Note : doing that, some questions were encountered in the way
tocptr and local_ep have (or do not have) to be copied/maintained
in storage.c canonicaliseSymtab



git-svn-id: svn://svn.valgrind.org/valgrind/trunk@14273 a5019735-40e9-0310-863c-91ae7b9d1cf9