cobat@ Fast implementations of logarithm function for base 2 and base e.

• FastLogf() and FastLog2f() - Accuracy: ~1.e-5, Speed: ~3x over logf()
• FasterLogf() and FasterLog2f() - Accuracy: ~1.e-3, Speed: ~6x over logf()
• FastestLogf() and FastestLog2f() - Accuracy: ~1.e-2, Speed: ~12x over logf()

Input check is supported only in Debug mode and is implemented via Y_ASSERT.