Replace intrcheck() by sigcheck() in many places.

In Pythonrun, tirn off SIGPIPE and move signal handlers elsewhere.
In ceval.c, also move locals_2_fast/ fast_2_locals to frameobject.c,
replaced local variable trace by f->f_trace, got rid of unused
mergelocals() and unneeded calls to fast_2_locals, return the variable
name on "fast variable not found", AND use "__call__" method if it
exists to call an inmstance.  Whew!