Fatal: Reusable trampolines

When a reusable "CORE" sub is leaked, compile and cache its trampoline
under the "Fatal" package rather than the original package[1].  This
allows autodie to trivially reuse the trampoline on leaks from other
packages as well.

[1] Note that the wrapper sub is compiled into "Fatal" as well when
the "CORE" sub is reusable.

Signed-off-by: Niels Thykier <niels@thykier.net>