sparc: define _GLOBAL_OFFSET_TABLE_ when referenced

GCC testsuite gcc.dg/20050321-2.c hit link errors on undefined
_GLOBAL_OFFSET_TABLE_.  The compiler output referenced only
_GLOBAL_OFFSET_TABLE_-offsets to set it up, and to compute the
GOT-relative address of local symbols, none of which triggered the
machinery that enabled the creation of the dynamic section, so
_GLOBAL_OFFSET_TABLE_ ended up undefined.

Enable the dynamic section if we find a relocation involving
_GLOBAL_OFFSET_TABLE_.  While at that, optimize checks for references
to it.


for  bfd/ChangeLog

	* elfxx-sparc.c (_bfd_sparc_elf_check_relocs): Check for
	_GLOBAL_OFFSET_TABLE_ references early, then compare hashed
	symbols instead of strings.
	(_bfd_sparc_elf_relocate_section): Compare hashed symbols.

for  ld/ChangeLog

	* testsuite/ld-sparc/got-def.s: New test.
	* testsuite/ld-sparc/sparc.exp: Add it.
5 files changed