sigcast turned into emit_obj_assign.
sigcast turned into emit_obj_assign.

The caller now omits sending the rhs sig, and instead checks that an object is wanted
before calling emit_obj_assign. sigcast was written a long time ago when it was thought
that other conversions might be necessary. This has not been the case, and at this point is
not likely to become the case. If it does become the case, then sigcast will be
resurrected. Until then, just ask to write an object assign.

FascinatedBox/lily,jesserayadkins/lily,FascinatedBox/lily,jesserayadkins/lily,FascinatedBox/lily,jesserayadkins/lily,FascinatedBox/lily