Look for a PT_GNU_RELRO section per object and, if present, mprotect that

Look for a PT_GNU_RELRO section per object and, if present, mprotect that
range instead of the [__got_start, __got_end) range.
On many archs this will cover _DYNAMIC too, so move up the DT_DEBUG handling
to before relocations and the mprotect are done.

ok kettenis@