Eliminate POSIX::int_macro_int, and all the complex AUTOLOAD fandango

Eliminate POSIX::int_macro_int, and all the complex AUTOLOAD fandango
that creates closures round it. Instead, wrap WEXITSTATUS, WIFEXITED,
WIFSIGNALED, WIFSTOPPED, WSTOPSIG and WTERMSIG directly with XS.
The shared library is slightly larger, but dynamic memory usage savings
beat this, even within one thread of one process. Simpler code too.

p4raw-id: //depot/perl@33896