Fixes to allow compile with Clang/OSX

The fixed_point bug also affects Linux, however it seems that code is not used yet.

As it stands, fixed_point instantiation such as results in IntBits being -25. Later when you left shift 1 << -25, g++ will give you zero while clang gives a negative value and fails.
fixed_point is also instantiated with long long, 1 << 44 results in zero (falloff) while again clang give negative value and fails.
This code will need to be changed before actually being used, as allocating an array of size 1<<44 is 16 Terabytes.