Fatal: Fix CORE leak trampoline for slurping args

When the prototype of a CORE sub has a slurping element, the generated
trampoline would fail to handle "extra" arguments.

Signed-off-by: Niels Thykier <niels@thykier.net>
Merge pull request #22 from nthykier/fix-core-leak-calls

Fatal: Fix CORE leak trampoline for slurping args