Added static RNGseed control
Don't change RNG in demos incase they are static
Make sure use_staticrng is false if not needed
Merge branch 'upstream' of https://github.com/Edward850/zdoom
- fixed: since A_LightGoesOut alters a sector's floor plane it must also alter the TexZ for that sector's floor.
Merge branch 'master' of https://github.com/rheit/zdoom
Merge branch 'gzdoom/master'