libntru 0.4

Changes since 0.3:

• massive performance improvements
• new Makefile targets for distros (thanks Julian Ospald)
• made the library C++ friendly (thanks Ruben De Smet)
• new functions: ntru_params_from_key_pair() and ntru_params_from_priv_key()
• fixed a memory leak
• fixed parameter values
• fixed data-dependent branches