New renderer implementation for Mob Spawning

Started to implement code to render the mob spawn conditions. It is similar to the old 1.6.3 style, but not completely the same. Still struggling with detecting mob spawninig conditions on opaque and semi transparent blocks. It seems, that the BlockInfo.flags information is not complete in the JSON description files.

I have reverted the "chunkcache.cpp" changes for 4K monitors for the moment. (No idea, how to exclude a single file from merge request...). When I succeed in a 64bit build I may do a second try there.

As general comment: it is best practice, not using TABs in source code. Much of the diff output below results just from simple formatting issues. So I would appreciate, if some master code owner replaces all TABs with spaces.