The value of AT_BASE should be the offset between where the ELF interpreter
expected to be loaded (as expressed in the ELF headers) and where it was
actually loaded, and not (as valgrind was doing) the absolute value of the
load address for the interpreter.

Note that when prelink is not in use the two are normally the same, as the
intpreter (like all shared libraries) is normally linked with a zero load
address. When prelinked that is no longer true.

With that fixed, the hack to patch out AT_BASE to avoid confusing gdb on
systems where prelink is in use is no longer needed.

Fixes BZ#329612


git-svn-id: svn://svn.valgrind.org/valgrind/trunk@13768 a5019735-40e9-0310-863c-91ae7b9d1cf9