Add newer ipc definitions for smd chip packages
As the title says, this adds the ipc definitions from the newer ipc7315b standard. The old 7315 definition is unchanged (other than removing a duplicate unneeded definition and adding an explanation about the fact that castelated exchanges the meaning of toe and heel in the ipc document.)
Footprint PR: https://github.com/KiCad/kicad-footprints/pull/642
Edited by Joel Guittet