Multithread the compiler.

- Added rudimentary multithreading to the method scheduler.
- Added locks to compilation and trace listeners so that GUI oriented
exceptions do not occur.
Merge pull request #118 from charsleysa/metadata

Multithread the compiler.
Merge branch 'master' of https://github.com/mosa/MOSA-Project
- Reverted multi-thread compiler (not ready yet).