* config/tc-mips.c (mips_5400): New variable.

* config/tc-mips.c (mips_5400): New variable.
(md_begin, md_parse_option): Handle 5400 options/names.
(macro_build, mips_ip): Check for 5400-specific instructions.
(md_longopts, OPTION_M5400, OPTION_NO_M5400): More command-line support for
5400.

* config/tc-mips.c (validate_mips_insn): New function, checks match versus mask
bits, and also verifies that all bits to be output are actually specified
somewhere.
(md_begin): Call it for 32-bit instructions, instead of doing match/mask check
here.  In case of failure, print a message, but check the rest of the opcode
table before exiting.