Some bits of COFF cleanup, and i960-coff support:

Some bits of COFF cleanup, and i960-coff support:

* config/obj-coff.h: Moved common includes and TARGET_FORMAT definitions
together.
(WORKING_DOT_WORD, WARN_SIGNED_OVERFLOW_WORD, OBJ_COFF_OMIT_OPTIONAL_HEADER,
BFD_HEADERS, BFD) [!BFD_ASSEMBLER]: Moved these definitions to the start of the
file, before the includes.
(SYMBOLS_NEED_BACKPOINTERS, OBJ_COFF_MAX_AUXENTRIES): Always define these.
(S_GET_ZEROES): Deleted.
(S_SET_ZEROES): Moved to obj-coff.c.

* config/obj-coff.c (obj_coff_* psuedo-op fns): Deleted forward declarations.
(obj_pseudo_table): Moved to one version end of file, conditionalized
internally.
(stack typedef, stack_init, stack_delete, stack_push, stack_pop, tag_hash,
tag_init, tag_insert, tag_find, tag_find_or_make): Moved to one combined
version at top of file, unconditional.  Deleted forward declarations.
(s_get_name): Moved one copy of declarations to start of file.
(def_symbol_in_progress): Ditto.  Don't initialize.
(S_SET_ZEROES): Moved here from obj-coff.h.
(write_object_file): If TC_COFF_SET_MACHINE is defined, call it on the file
headers.

* config/obj-coff.c (seg_info_off_by_4): Now const and static.
(SEG_INFO_FROM_SEG_NUMBER): Unused macro deleted.
(previous_file_symbol, def_symbol_in_progress, symbol_externP,
symbol_extern_lastP, last_functionP) [!BFD_ASSEMBLER]: Don't bother explicitly
initializing to zero value.

* config/obj-coff.c (fixup_segment) [TC_I960]: Use SF_GET_BALNAME and
SF_GET_CALLNAME instead of the TC_S_IS_ versions.