Separated out opcode aliases from m68k opcode table, to reduce table size and

Separated out opcode aliases from m68k opcode table, to reduce table size and
processing time.  Aliases are now a separate table.

* m68k.h (enum m68k_architecture): Deleted.
(struct m68k_opcode_alias): New type.
(m68k_opcodes): Now const.  Deleted opcode aliases with exactly matching
constraints, values and flags.  As a side effect of this, the
MOTOROLA_SYNTAX_ONLY and MIT_SYNTAX_ONLY macros, which so far as I know were
never used, now may need re-examining.
(numopcodes): Now const.
(m68k_opcode_aliases, numaliases): New variables.
(endop): Deleted.
[DONT_DEFINE_TABLE]: Declare numopcodes, numaliases, and m68k_opcode_aliases;
update declaration of m68k_opcodes.