Improve finite liquid distribution, fix small bug
Don't rebuild the dummy shader (less SourceShaderCache warning spam)

Also write something about rebuilding shaders to infostream in
Client::afterContentReceived()
Fix possible NULL dereference in createExtrudedMesh
Mapgen V7: Huge rewrite, also tweaks to cavegen et al.
Use hexadecimal RRGGBB instead of colorkeys, rename getColor to parseColor