Fix some PowerPC VLE BFD issues and add some PowerPC VLE instructions.

    Fix some PowerPC VLE BFD issues and add some PowerPC VLE instructions.

        bfd/
        * elf32-ppc.c (is_branch_reloc): Recognise VLE branch relocations.
        (ppc_elf_howto_raw): Fix dst_mask of R_PPC_VLE_REL15.
        (ppc_elf_vle_split16): Clear field before inserting.

        opcodes/
        * ppc-opc.c (vle_opcodes): Alias 'e_cmpwi' to 'e_cmpi' and
        'e_cmplwi' to 'e_cmpli' instead.
        (OPVUPRT, OPVUPRT_MASK): Define.
        (powerpc_opcodes): Add E200Z4 insns.
        (vle_opcodes): Add context save/restore insns.

        include/
        * opcode/ppc.h (PPC_OPCODE_E200Z4): New define.