instruction registers, opcodes and formats. Build internal table
for new instructions and provide callbacks for assembler and
disassembler.
* itbl-lex.l, itbl-parse.y: Lex and yacc parsers for instruction
spec table.
* itbl-ops.h: New file. Header file for itbl support.
* config/itbl-mips.h: New file. Mips specific definitions for
itbl support.
