This update is focused on improving the throughput of the Costas loop, however some changes are more global performance enhancements as this PR has evolved. Updates include an ENABLE_NATIVE added to CMake, which is off by default but enables native compiling (including FMA support) if desired; sincos was inlined in sincos.h and sincos.cc was removed from the appropriate CMake to improve sincos speed, some constants were added to math.h, inlined functions in costas loop and nco.h, used switch instead of function pointer (much faster), and used fast complex multiply to get around all the range checking in the standard complex.h complex multiply function on all builds.