* GLES Shaders and Vulkan Clip fallback
* clip fallback: change defined name, set from engine side and invert usage
* Proposed changes and fixes
Fixed:
-The OpenGL ES option stays on when OpenGL is off (issue #7984)
-Missing precision in copy-f, volumetric-f and smaa-resolve-f
-msaa-f including z-compress before precision quantification
-missing float literals in volumetric-f
-Fixed decals blending
-Restored glBindFragDataLocation() for use in legacy external shaders
-Enabled GL_ARB_explicit_attrib_location ext for GLSL version below 330 in GL
-Guarded enabling/disabling of GL_CLIP_DISTANCE0_EXT and GL_DEPTH_CLAMP
-Restored PI in lighting.sdr
-removed "External shaders only" indication from cmakelists.txt