Merge branch 'release/materials_featurette' into marchcat/x-mf-merge

doc/testplans/pbr_terrain_appearance.md

...settings/shaders/class1/deferred/pbrShadowAlphaMaskF.glsl

...view/app_settings/shaders/class1/deferred/pbropaqueF.glsl

...iew/app_settings/shaders/class1/deferred/pbrterrainV.glsl

...ew/app_settings/shaders/class1/deferred/textureUtilV.glsl

..._settings/shaders/class1/windlight/atmosphericsFuncs.glsl

indra/newview/lldrawpoolterrain.cpp

indra/newview/llface.cpp

indra/newview/llfetchedgltfmaterial.cpp