[PATCH 2/4] The main m68k cc0 conversion

[Bernd Schmidt]

This achieves the conversion by using combined cbranch/cstore patterns,
and using a mechanism similar to the cc_status tracking to elide certain
comparisons.  Unlike cc_status, this is opt-in and requires a
flags_valid attribute to be set for suitable instructions.  Due to lack
of test hardware, this conversion is omitted for a number of coldfire
patterns as opposed to normal m68k.

For DImode comparisons, scc_di and beq0_di/bne0_di patterns already
existed and are reused.  The bgt0_di/ble0_di patterns are replaced with
expander code to test just the high word, along with some smarts in
m68k_find_flags_value.


Bernd