Shaders rework.

builtin/mainmenu.lua

client/shaders/alpha_shader/base.txt

client/shaders/alpha_shader/opengl_fragment.glsl

client/shaders/alpha_shader/opengl_vertex.glsl

client/shaders/bumpmaps_liquids/opengl_fragment.glsl

client/shaders/bumpmaps_solids/opengl_fragment.glsl

client/shaders/leaves_shader/base.txt

client/shaders/leaves_shader/opengl_fragment.glsl

client/shaders/leaves_shader/opengl_vertex.glsl

client/shaders/liquids_shader/base.txt

client/shaders/liquids_shader/opengl_fragment.glsl

client/shaders/liquids_shader/opengl_vertex.glsl

client/shaders/plants_shader/base.txt

client/shaders/plants_shader/opengl_fragment.glsl

client/shaders/plants_shader/opengl_vertex.glsl

client/shaders/solids_shader/base.txt

client/shaders/solids_shader/opengl_fragment.glsl

client/shaders/solids_shader/opengl_vertex.glsl

client/shaders/test_shader_1/opengl_fragment.glsl

client/shaders/test_shader_2/opengl_fragment.glsl