Since GCC 5 folds symbol address comparison, assuming each symbol has a
different address, &foo == &bar is always false for GCC 5. This patch
adds check_ptr_eq if 2 addresses are the same and uses it to check the
address of versined symbol.
PR ld/18718
* ld-elf/check-ptr-eq.c: New file.
* ld-elf/pr18718.c (main): Call check_ptr_eq.
* ld-elf/shared.exp: Add check-ptr-eq.c to PR ld/18718 tests.
