* inferior.h: Eliminate CANNOT_EXECUTE_STACK in favor of

* inferior.h:  Eliminate CANNOT_EXECUTE_STACK in favor of
defining CALL_DUMMY_LOCATION as BEFORE_TEXT_END.  This is
because machines that do this will also have to know to
set NEED_TEXT_START_END.  Besides, it was a redundant way to
say the same thing.
* tm-29k.h, tm-convex.h, tm-np1.h:  Eliminate
CANNOT_EXECUTE_STACK, define CALL_DUMMY_LOCATION and
NEED_TEXT_START_END.