bfd signed overflow fixes

Aimed at quietening ubsan.

include/
	* opcode/mmix.h (PUSHGO_INSN_BYTE): Make unsigned.
	(GO_INSN_BYTE, SETL_INSN_BYTE, INCML_INSN_BYTE, INCMH_INSN_BYTE),
	(INCH_INSN_BYTE, SWYM_INSN_BYTE, JMP_INSN_BYTE): Likewise.
bfd/
	* elf32-rx.c (elf32_rx_relax_section): Avoid signed overflow.
	* libaout.h (N_SET_INFO, N_SET_FLAGS): Likewise.
	* netbsd.h (write_object_contents): Likewise.
	* elf32-arm.c (bfd_elf32_arm_vfp11_erratum_scan): Likewise.
	* libhppa.h (HPPA_R_CONSTANT): Don't signed extend with shifts.
	(stm32l4xx_create_replacing_stub_vldm): Don't truncate high bits
	with shifts.
	* elf32-nds32.h (R_NDS32_RELAX_ENTRY_DISABLE_RELAX_FLAG): Define
	using 1u shifted left.  Ditto for other macros.
	* mmo.c (LOP): Make unsigned.