Changed Mesa backend to output GLSL ES 3.00 in order to support shadow mapping
Disabled shadow mapping for Mesa drivers fixes #103
Patched GLEW to get the extensions with OpenGL >= 3.2 for the case that glGetString(GL_EXTENSIONS) fails
Removed glewExperimental = GL_TRUE hack for SDL 2
Added r_forceShadowMapsOnAlphaTestedSurfaces 1
Updated embedded shaders
Updated ENGINE_VERSION
Added shadow LOD calculation
Improved shadow mapping performance using the shadow LOD and tweaked
polygon offsets to fight shadow acne
Shadow LOD fix for parallel lights
Fixed problems when building for Win64 and using FFmpeg. fixes #106
Fixed shadow mapping problems with the ATI Catalyst driver
Reduced FFmpeg debug console prints
Made interactionSM shader sampler loop to use r_shadowMapSamples many iterations
Only use 2048^2 shadow maps for cascaded shadow mapping
Made interactionSM shader sampler loop to use r_shadowMapSamples many iterations
Supress warnings about failed #include global.inc when using embedded Cg shaders
Added custom content support by looking for all content in all maps/*.resources.

This changes the filesystem to work a bit more like previous id tech
engines and allows to run mods and custom content like the Wulfen high
resolution textures in those mods with

+set fs_game <modname> +set fs_resourceLoadPriority 0
Changed file testing for .bik videos to support fs_game. fixes #100
Fixed typo. Now all videos should work on Linux. refs #100