This patch removes set-but-unused variables.  This holds all the
removals I consider to be simple and relatively uncontroversial.

2016-07-14  Tom Tromey  <tom@tromey.com>

	* mips-tdep.c (micromips_scan_prologue): Remove "frame_addr".
	(mips_o32_push_dummy_call): Remove "stack_used_p".
	* aarch64-tdep.c (aarch64_record_data_proc_imm): Remove
	"insn_bit28".
	* rust-lang.c (rust_print_type): Remove "len".
	* rust-exp.y (super_name): Remove "current_len".
	* python/py-framefilter.c (py_print_type): Remove "type".
	* mdebugread.c (parse_partial_symbols): Remove
	"past_first_source_file".
	<N_SO>: Remove "valu", "first_so_symnum", "prev_textlow_not_set".
	* m2-valprint.c (m2_print_unbounded_array): Remove
	"content_type".
	(m2_val_print): Remove "i".
	* linespec.c (unexpected_linespec_error): Remove "cleanup".
	* f-valprint.c (f_val_print): Remove "i".
	* elfread.c (elf_symtab_read): Remove "offset".
	* dwarf2-frame.c (dwarf2_fetch_cfa_info): Remove "addr_size".
	* jit.c (jit_dealloc_cache): Remove "i" and "frame_arch".