- warning fixes

 - first block might have more than one predecessor

add support for Exceptions
some typos fixed

be_main now gets filename passed from frontend

  runtime. be_verify_register_allocation should find the same errors anyway...
- fixes for block schedule creation

  of the backend stuff
- Calculate execution frequencies for all irgs early
- Commented out set_Debug stuff in javacoal because it was broken
- Use new execfreq extbb calculation
- some warning fixes