Prepare gas for 64-bit obstacks

Prepare gas for 64-bit obstacks

Use size_t in a few places involved with obstacks, and don't include
obstack.h in files that don't use obstacks.

gas/
	* config/bfin-parse.y: Don't include obstack.h.
	* config/obj-aout.c: Likewise.
	* config/obj-coff.c: Likewise.
	* config/obj-som.c: Likewise.
	* config/tc-bfin.c: Likewise.
	* config/tc-i960.c: Likewise.
	* config/tc-rl78.c: Likewise.
	* config/tc-rx.c: Likewise.
	* config/tc-tic4x.c: Likewise.
	* expr.c: Likewise.
	* listing.c: Likewise.
	* config/obj-elf.c (elf_file_symbol): Make name_length a size_t.
	* config/tc-aarch64.c (symbol_locate): Likewise.
	* config/tc-arm.c (symbol_locate): Likewise.
	* config/tc-mmix.c (mmix_handle_mmixal): Make len_0 a size_t.
	* config/tc-score.c (s3_build_score_ops_hsh): Make len a size_t.
	(s3_build_dependency_insn_hsh): Likewise.
	* config/tc-score7.c (s7_build_score_ops_hsh): Likewise.
	(s7_build_dependency_insn_hsh): Likewise.
	* frags.c (frag_grow): Make parameter a size_t, and use size_t locals.
	(frag_new): Make parameter a size_t.
	(frag_var_init): Make max_chars and var parameters size_t.
	(frag_var, frag_variant): Likewise.
	(frag_room): Return a size_t.
	(frag_align_pattern): Make n_fill parameter a size_t.
	* frags.h: Update function prototypes.
	* symbols.c (save_symbol_name): Make name_length a size_t.