-Wimplicit-fallthrough error fixes

-Wimplicit-fallthrough error fixes

Well, not all are errors, but a little more substantive than just
fiddling with comments.

bfd/
	* coffcode.h (coff_slurp_symbol_table): Revert accidental commit
	made 2015-01-08.
	* elf32-nds32.c (nds32_elf_grok_psinfo): Add missing break.
	* reloc.c (bfd_default_reloc_type_lookup): Add missing breaks.
opcodes/
	* arc-ext.c (create_map): Add missing break.
	* msp430-decode.opc (encode_as): Likewise.
	* msp430-decode.c: Regenerate.
binutils/
	* coffdump.c (dump_coff_where): Add missing break.
	* stabs.c (stab_xcoff_builtin_type): Likewise.
gas/
	* config/tc-arc.c (find_opcode_match): Add missing break.
	* config/tc-i960.c (get_cdisp): Likewise.
	* config/tc-metag.c (parse_swap, md_apply_fix): Likewise.
	* config/tc-mt.c (md_parse_option): Likewise.
	* config/tc-nds32.c (nds32_apply_fix): Likewise.
	* config/tc-hppa.c (pa_ip): Assert rather than testing last
	condition of multiple if statements.
	* config/tc-s390.c (s390_exp_compare): Return 0 on error.
	* config/tc-tic4x.c (tic4x_operand_parse): Add as_bad and break
	out of case rather than falling into next case.  Formatting.
ld/
	* plugin.c (asymbol_from_plugin_symbol): Avoid compiler warning
	by adding return.