Fix a minor bug (ORo didn't mark that it set CR0).

Refactor how . instructions are handled.  In particular, instead of passing
the RC flag all the way up the inheritance hierarchy, just make a new tblgen
class 'DOT' which can be added to an instruction definition.

For example, instead of this:

-def AND  : XForm_6<31,  28, 0, 0, 0, (ops GPRC:$rA, GPRC:$rS, GPRC:$rB),
-let Defs = [CR0] in
-def ANDo : XForm_6<31,  28, 1, 0, 0, (ops GPRC:$rA, GPRC:$rS, GPRC:$rB),
-                   "and. $rA, $rS, $rB">;

We now have this:

+def AND  : XForm_6<31,  28, 0, 0, (ops GPRC:$rA, GPRC:$rS, GPRC:$rB),
                    "and $rA, $rS, $rB">;

llvm-svn: 21225