PowerPC32 treatment of absolute symbols

As already done for PowerPC64, fix dynamic relocs for absolute symbols.
The patch also tidies the dynamic reloc handling code in check_relocs,
removing leftover comments and code from when check_relocs was called
as each object file was read in.

bfd/
	* elf32-ppc.c (ppc_elf_check_relocs): Set isym and ifunc earlier.
	Rearrange tests for dynamic relocs, handling absolute symbols.
	(allocate_dynrelocs): Don't allocate dynamic relocs for locally
	defined absolute symbols.
	(ppc_elf_size_dynamic_sections): Similarly.
	(ppc_elf_relocate_section): Similarly.
ld/
	* testsuite/ld-powerpc/abs32-pie.d,
	* testsuite/ld-powerpc/abs32-pie.r,
	* testsuite/ld-powerpc/abs32-reloc.s,
	* testsuite/ld-powerpc/abs32-shared.d,
	* testsuite/ld-powerpc/abs32-shared.r,
	* testsuite/ld-powerpc/abs32-static.d,
	* testsuite/ld-powerpc/abs32-static.r: New tests.
	* testsuite/ld-powerpc/powerpc.exp: Run them.