BF - older C compilers do not have round in math.h, uisng dpy_math instead
BF: define our own round for c++98 compatibility
BF: round to nearest even
BF: use define and use dpy_signbit instead of signbit. Use dpy_rint instead of round.
BF: use npy_* functions directly instead of defining our own dpy_* versions
Use NPY_PI instead of DPY_PI
Merge pull request #494 from omarocegueda/fix_round

Fix round