Bugfix: Compound ops with a global was a crasher.

Before running a compound op, check if it's a global. If it's a global, then
it needs to be loaded into a local register before being worked with.

Added a test to pre-commit-hook.py, because this was causing crashes.
Change <@lily to <?lily, @> to ?>. Fixes #46.

The newer format is valid xml, and thus can be checked with an xml validator.