* configure.in (i960-*-coff, i960-*-vxworks5.*): Use coffbfd, and gas_target

* configure.in (i960-*-coff, i960-*-vxworks5.*): Use coffbfd, and gas_target
ic960coff.
* config/ic960coff.mt: New file.
* config/obj-coffbfd.h [TC_I960]: Include coff/i960.h.
(TARGET_FORMAT) [TC_I960]: Use coff-Intel-little.
* config/te-ic960.h (CROSS_COMPILE): Don't undef this.  We'll always build
little-endian object files.
* config/tc-i960.c (md_reloc_size): Don't define at all if BFD or
BFD_ASSEMBLER is defined.
(mem_fmt): Since COFF doesn't handle callx relocations yet, treat them like
normal 32-bit relocations.
(md_apply_fix): For callx relocations, store zero.
(tc_bout_fix_to_chars): Store symbol idx for all callx relocations, regardless
of link-relax setting.
(tc_coff_fix2rtype, tc_coff_sizemachdep): New functions.
(i960_handle_align) [! OBJ_BOUT]: If link-relax option is selected, print an
error message and clear it.
* config/tc-i960.h (BFD_ARCH, COFF_FLAGS, COFF_MAGIC, TC_COUNT_RELOC,
TC_COFF_FIX2RTYPE, TC_COFF_SIZEMACHDEP, tc_fix_adjustable): New macros.
(tc_coff_fix2rtype, tc_coff_sizemachdep): Declare.