Taking an undefined function's address in an executable

Taking an undefined function's address in an executable

doesn't always mean you need to define a function symbol on plt code.
If all references are in read-write sections, then using dynamic relocs
is OK.

bfd/
	* elf32-ppc.c (ppc_elf_adjust_dynamic_symbol): Clear
	pointer_equality_needed when !readonly_dynrelocs.
	* elf64-ppc.c (ppc64_elf_adjust_dynamic_symbol): Likewise.
ld/testsuite/
	* ld-powerpc/ambiguousv1.d: Match symbol table too.
	* ld-powerpc/ambiguousv2.d: Likewise.
	* ld-powerpc/ambiguousv1b.d: New.
	* ld-powerpc/ambiguousv2b.d: New.
	* ld-powerpc/powerpc.exp: Run new tests.