REVERTED: Removed the need for rlMatrix

Now rlgl uses the `Matrix` type, just make sure it has been previously defined somewhere... I don't like this approach but it's probably the easier one for the users... still looking for a better solution... maybe using something like
`#define MATRIX_TYPE`, so it can be checked in other modules.

examples/shaders/shaders_hot_reloading.c

@@ -77,7 +77,7 @@ int main(void)
                 // Try reloading updated shader
                 Shader updatedShader = LoadShader(0, TextFormat(fragShaderFileName, GLSL_VERSION));
 
-                if (updatedShader.id != rlGetShaderDefault().id)      // It was correctly loaded
+                if (updatedShader.id != rlGetShaderIdDefault())      // It was correctly loaded
                 {
                     UnloadShader(shader);
                     shader = updatedShader;