PowerPC64 undefined weak visibility vs GOT optimisation

PowerPC64 undefined weak visibility vs GOT optimisation

Undefined weak symbols with non-default visibility are seen as local
by SYMBOL_REFERENCES_LOCAL.  This stops a got indirect to relative
optimisation for them, so that pies and dlls don't get non-zero values
when loading somewhere other than the address they are linked at
(which always happens).  The optimisation could be allowed for pdes,
but I thought it best not to allow it there too.

bfd/
	* elf64-ppc.c (ppc64_elf_relocate_section): Don't optimise got
	indirect to pc-relative or toc-relative for undefined symbols.
ld/
	* testsuite/ld-powerpc/weak1.d,
	* testsuite/ld-powerpc/weak1.r,
	* testsuite/ld-powerpc/weak1.s,
	* testsuite/ld-powerpc/weak1so.d,
	* testsuite/ld-powerpc/weak1so.r: New tests.
	* testsuite/ld-powerpc/powerpc.exp: Run them.