* Slots for custom post processing effects
Post processing effects such as tint or dithering have their uniforms hardcoded, which means the only want to create new post-process effects for a mod is to overwrite an existing effect.
Requested for DEM2, this PR creates 4 blank slots for mods to create new post processing effects--2 floats and 2 vec3. This approach to create blank slots for modders follows the successful strategy used for Custom_Controls 1-5.
Note, this PR also adds `tint` to the default `post_processing.tbl` which had it missing (even though tint is a valid effect with a valid uniform buffer already).
Happy to discuss more or edit however.
* fix ordering
This can be used for producing even leaner builds for standalone
servers. It also provides a nice architecture verification since now
using internal OpenGL functions will cause a compilation or linking
failure.
wookieejedi