clean up core.ops

The situation with set vs. set_keyed vs. set_keyed_integer is pretty foul
now.  The last half of core.ops has a bunch of set() functions and,
corresponding to (most of) them, set_keyed_integer() functions with the
exact same arguments and bodies.  From what I gather, the 3-argument set()
functions are a relic from the old assembler syntax (before "Px[Ix]"), and
should not be used.  Unless anyone objects quickly, the three-arg sets
will be gone.  This will break older code (e.g. t/pmc/array.t).  If
someone wants to submit either a patch to the assembler to handle this, or
patches upgrading old code to the new syntax... well, you know what to
do.

/s

• clean up core.ops by Sean O'Rourke
• Re: clean up core.ops by Dan Sugalski