fast_gamma is suppressed as it is neither fastest nor more accurate as the final gamma
adding also tests in the right ranges
fast_gamma was not removed from bench lists
bad ranges for stirling covers
added/reordered unit for gamma
removing trailing references to fast_gamma
coherency of stirling covers
using cephes_gamma in exhaustive gamma test
Merge pull request #721 from jtlap/improve_gamma

Improve gamma