Removing old tests that are now in the benchmarks.
Adding GC plugin for LLVM.

This also includes a very trivial test. The plugin is still quite unfinished.
Tagging functions with the qsgc collector.

Also updating the qsc in the tests directory to use the plugin
during llc compilation.

The Makefile now also uses the 'system' qsc rather than the local one,
to guarantee that the qsc used elsewhere is also used in the tests.