sha1collisiondetection

This is a large cleanup version:

• removed unused recompression functions and uses switch instead of a lookup table
• non-api functions are now static and not exported anymore
• compiles in c90 standard
• removed SIMD for now:
  this was still WIP and still missed runtime selection code.
  Work on this has been moved to simd branch
• Makefile rewrite:
  • Added install target
  • Support for libtool-less systems

It is still marked as development for now, as naming might still change.

Thanks to all who have contributed!