Fix sh-elf linker relaxation:

Fix sh-elf linker relaxation:

gcc:
	* config/sh/sh.h (EXTRA_SPECS): Add subtarget_asm_relax_spec and
	subtarget_asm_isa_spec.
	(SUBTARGET_ASM_RELAX_SPEC, SUBTARGET_ASM_ISA_SPEC): Define.
	(ASM_SPEC): Define as SH_ASM_SPEC.
	(SH_ASM_SPEC): New; take the role of ASM_SPEC, but safe from svr4.h.
	Use subtarget_asm_relax_spec and subtarget_asm_isa_spec.
	* config/sh/elf.h (ASM_SPEC): Use SH_ASM_SPEC.
	(SUBTARGET_ASM_ISA_SPEC): Undef / define.
gcc/testsuite:
	gcc.dg/sh-relax.c: New test.

include/elf:
	* sh.h (EF_SH_MERGE_MACH): Make sure SH2E & SH3/SH3E merge to SH3E,
	and SH2E & SH4 merge to SH4, not SH2E.

gas:
	* config/tc-sh.c (sh_dsp): Replace with preset_target_arch.
	(md_begin): Use preset_target_arch.
	(md_longopts): Make isa option unconditional.
	(md_parse_option): Make OPTION_DSP and OPTION_ISA sh4 / any
	set preset_target_arch.
	(md_apply_fix3): If BFD_ASSEMBLER, adjust SWITCH_TABLE fixups
	by -S_GET_VALUE  (fixP->fx_subsy).
	(tc_gen_reloc): For SWITCH_TABLE fixups, the symbol is fixp->fx_subsy,
	and the addend is 0.
	Adjust addend of R_SH_IND12W relocations by fixp->fx_offset - 4.
	* config/tc-sh.h (TC_FORCE_RELOCATION_SUB_LOCAL): Define.

bfd:
	elf32-sh.c (sh_elf_howto_tab): Make R_SH_IND12W into an ordinary
	relocation (no special function), and make it non-partial_inplace.
	(sh_elf_relax_section): When creating a bsr, use a consistent value
	no matter if the symbol is extern or not;  set addend to -4.
	Don't swap load / non-load instructions for SH4.
	(sh_elf_relax_delete_bytes): In R_SH_IND12W case, check the offset
	rather than if the symbol is external to determine if adjusting the
	offset makes sense.  Adjust the addend too if appropriate.
	(sh_elf_relocate_section): In R_SH_IND12W, don't fiddle with the
	relocation.