PowerPC64 paddi -Mraw

PowerPC64 paddi -Mraw

On a testcase like
 pla 8,foo@pcrel
disassembled with -Mpower10 results in
   0:	00 00 10 06 	pla     r8,0	# 0
   4:	00 00 00 39
			0: R_PPC64_PCREL34	foo
but with -Mpower10 -Mraw
   0:	00 00 10 06 	.long 0x6100000
			0: R_PPC64_PCREL34	foo
   4:	00 00 00 39 	addi    r8,0,0

The instruction is unrecognised due to the hack we have in
extract_pcrel0 in order to disassemble paddi with RA0=0 and R=1 as
pla.  I could have just added "&& !(dialect & PPC_OPCODE_RAW)" to the
condition in extract_pcrel0 under which *invalid is set, but went for
this larger patch that reorders the extended insn pla to the more
usual place before its underlying machine insn.  (la is after addi
because we never disassemble to la.)

gas/
	* testsuite/gas/ppc/raw.d,
	* testsuite/gas/ppc/raw.s: Add pla.
opcodes/
	* ppc-opc.c (extract_pcrel1): Rename from extract_pcrel0 and
	invert *invalid logic.
	(PCREL1): Rename from PCREL0.
	(prefix_opcodes): Sort pla before paddi, adjusting R operand
	for pla, paddi and psubi.