Add functions

Functions:
pie_dPoint3D.h
	+ pie_dPoint3DCross
	pie_dPoint3DSum -> pie_dPoint3DMul (wft?)

Add some comments
Revert "Add functions"

This reverts commit 3c3a03bb036d8ee0bebd2d759278433f87668258.
Merge branch 'master' of https://github.com/pierceheavens/pie
Forgot to rename function

at pie_dPoint3D.c
	pie_dPoint3DSum -> pie_dPoint3DMul