Blender Git Loki

BGE : Collision mask support in raycast + and raycast cleanup.

I have removed the m_pHitObject, m_xray and m_testPropName and replace them by a temporary struct "RayCastData" which contains these datas and a collision mask. Finally i add a collision mask argument in the python function "rayCast" :
```
rayCast(to, from, dist, prop, face, xray, poly, mask)
```

It can be useful to hit only object which are on the right colision layer. for example if you have hitbox for a charater or vehicle you don't want to hit it with raycast.

test file : {F237337}
left mouse click on two planes and see console messages.

Somewhat more elaborate test file by @sybren: {F237779}
Look around and click on the cubes. One cube lamp responds, the other doesn't, based on their collision groups.

Reviewers: moguri, hg1, agoose77, campbellbarton, sybren

Reviewed By: agoose77, campbellbarton, sybren

Subscribers: campbellbarton, sergey, blueprintrandom, sybren

Projects: #game_engine, #game_physics

Differential Revision: https://developer.blender.org/D1239