* bltinmodule.c: added built-in function cmp(a, b)

* flmodule.c: added {do,check}_only_forms to fl's list of functions;
  and don't print a message when an unknown object is returned.

* pythonrun.c: catch SIGHUP and SIGTERM to do essential cleanup.

* Made jpegmodule.c smaller by using getargs() and mkvalue() consistently.

* Increased parser stack size to 500 in parser.h.

* Implemented custom allocation of stack frames to frameobject.c and
  added dynamic stack overflow checks (value stack only) to ceval.c.
  (There seems to be a bug left: sometimes stack traces don't make sense.)