Add my own math library

GLM works only for C++ and I plan on moving to back to C. There is
a C port, but it would be good for me to figure out vertex math myself.
Hence, my own library has been created.

dependencies.dep

@@ -1,8 +1,3 @@
-[GLM]
-git_url = https://github.com/g-truc/glm.git
-tag = 0.9.9.8
-custom_commands = cd GLM && mkdir build && cd build && cmake .. -D BUILD_SHARED_LIBS=ON && make && cd .. && mkdir include && mv glm include
-
 [GLFW]
 git_url = https://github.com/glfw/glfw.git
 tag = 3.3.8