Add wielded (and CAOs) shader

client/shaders/wielded_shader/opengl_fragment.glsl

client/shaders/wielded_shader/opengl_vertex.glsl

src/camera.cpp

src/camera.h

src/client/tile.cpp

src/client/tile.h

src/mesh.cpp

src/mesh.h

src/nodedef.cpp

src/wieldmesh.cpp

src/wieldmesh.h