pmruntime(): rename var to avoid macro name clash

[perl #116557]

Apparently MS's WinCE SDK #defines 'leave'. So rename the 'leave' variable
to 'leaveop' to avoid clashes.
pmruntime(): change '=' to '==' in an assertion

Whoops!

Probably harmless, since if the thing it was intended to assert for
was indeed true, then the assignment would be a noop anyway.