[SCons] Build with Solid as default when enabling the gameengine in the build process
[SCons] Build solid and qhull from the extern directory and link statically against them
That was about it.
There are a few things that needs double checking:
* Makefiles
* Projectfiles
* All the other systems than Linux and Windows on which the build (with scons) has been successfully tested.
(MVert,MFace,etc) off into DNA_meshdata_types.h, to isolate areas
of source that actually edit mesh *data* vs. areas that just edit
mesh object information.
