Previously dlsym resolved to the version in crt0.o or libc which would
mean that the caller's shared object couldn't be determined correctly
using __builtin_return_address(0).
Mainly from FreeBSD, but adapted by me. Benefits of this solutions are:
- backward comptibility maintained
- existing broken binaries are fixed with a new ld.elf_so
- __mainprog_obj can be removed from crt0.o
- we do the same thing as FreeBSD
Fixes PR 22067.
OKed by Jason and Christos.
skrll