Linux customshader compilation fix

Fix of an issue with custom shaders from mb not compiling due to different shader compilation behavior on windows and linux regarding absence of #version directive by:

• displaying a warning message if custom shader is loaded not containing #version directive to hint to modders of potential issues it might bring
• trying to prepend #version and compile custom shaders from latest 330 GLSL version to oldest 110 version

added 1 commit

• fb437a3c - white space fix

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approved this merge request

requested review from @Alam

added OpenGL renderer label

added 2 commits

• dfb57319 - 1 commit from branch STJr:next
• 064e2cb7 - Merge branch SRB2:next into linux-customshader-compilation-fix

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added 3 commits

• 064e2cb7...488e6d56 - 2 commits from branch STJr:next
• f291c846 - Merge branch SRB2:next into linux-customshader-compilation-fix

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merged

mentioned in commit 7c4442a3