Improvements requiring the base game

Autor : alufolie91

This build should hopefully address all the regressions introduced in v6

IMPORTANT NOTE:
If your GPU does not support Opengl 3.0 or crashes on startup (which hopefully shouldnt happen) in OpenGL mode
or simply aint interested in the feature
Use the non FBO version!

• Optimization to Weather Rendering, now it actually should perform better with shorter precip distance (Render Weather through the Blockmap instead of BSP traversal;also made precip distance be properly affected by mobjscaled maps)
• Fixed some issues with FOF rendering (Laboratory Takeover from Assault Pack should look normal again;No more weird Fog)
• Add IT_CV_BIGFLOAT to use bigger increment for some CV_FLOAT cvars (FOV and Driftgauge offset from the menu now wont take ages to change)
• Dont call menu drawer in wipes on dedicated servers (fixes a rare crash)
• Fix a possible overflow in va function (should prevent some crashes)
• Fix some issues with CV_FLOAT cvars / For MIN/MAX value of cvar, convert it to float before saving for CV_FLOAT variables
• Fixed a rare crash with weather
• Disabling screen textures now will also disable Palette rendering if its enabled, to prevent visual issues from occuring
• Multiple smaller code fixes
• Fixed cmake building (hopefully)
• Made FixedRem function more performant

FBO BUILD ONLY

• Support to downsample from a higher resolution than your current display resolution in OpenGL using Framebuffer Objects
  Note: This requires a GPU that atleast supports OpenGL version 3.0
  Compile Note: by default this feature is enabled to be build with the game, using the NOSCREENFBO compiler flag will build without support for OpenGL downsampling

Thanks again to everyone who helped making Saturn to what it is now, and also thanks to everyone who enjoyed our work!