gas signed overflow fixes

gas signed overflow fixes

	* config/tc-aarch64.c (get_aarch64_insn): Avoid signed overflow.
	* config/tc-metag.c (parse_dalu): Likewise.
	* config/tc-tic4x.c (md_pcrel_from): Likewise.
	* config/tc-tic6x.c (tic6x_output_unwinding): Likewise.
	* config/tc-csky.c (parse_fexp): Use an unsigned char temp buffer.
	Don't use register keyword.  Avoid signed overflow and remove now
	unneccesary char masks.  Formatting.
	* config/tc-ia64.c (operand_match): Don't use shifts to sign extend.
	* config/tc-mep.c (mep_apply_fix): Likewise.
	* config/tc-pru.c (md_apply_fix): Likewise.
	* config/tc-riscv.c (load_const): Likewise.
	* config/tc-nios2.c (md_apply_fix): Likewise.  Don't potentially
	truncate fixup before right shift.  Tidy BFD_RELOC_NIOS2_HIADJ16
	calculation.