Copied "fast math" utilities over from commons-math v3.1.1.

I copied this into the project so I wouldn't have to depend on
commons-math for only these utilities.  I had to make a few changes to
the original sources in order to get them to compile outside their home.
Eclipse files are now ignored.
Added copyright notice for the files pulled from commons-math.
Added code for computation of fast inverse square roots.

The algorithm I used is an adapted version of Greg Walsh's algorithm
described here:

http://en.wikipedia.org/wiki/Methods_of_computing_square_roots#Reciprocal_of_the_square_root

This is also commonly known as the inverse square root from Quake 3.