Implement a global shader parameter passing system and useful shaders

client/shaders/test_shader_1/base.txt

client/shaders/test_shader_1/opengl_fragment.glsl

client/shaders/test_shader_1/opengl_vertex.glsl

client/shaders/test_shader_2/.opengl_fragment.glsl.swo

client/shaders/test_shader_2/base.txt

client/shaders/test_shader_2/opengl_fragment.glsl

client/shaders/test_shader_2/opengl_vertex.glsl

client/shaders/the_darkness_of_light/opengl_fragment.asm

client/shaders/the_darkness_of_light/opengl_fragment.glsl

client/shaders/the_darkness_of_light/opengl_vertex.asm

src/game.cpp

src/mapblock_mesh.cpp

src/shader.cpp

src/shader.h