Cleanup

Thanks to glfwGetKeyScancode we can now pass only a scancode to the
platform layer for glfwGetKeyName.

src/mir_window.c

@@ -830,7 +830,7 @@ void _glfwPlatformSetCursorMode(_GLFWwindow* window, int mode)
     }
 }
 
-const char* _glfwPlatformGetKeyName(int key, int scancode)
+const char* _glfwPlatformGetScancodeName(int scancode)
 {
     _glfwInputError(GLFW_PLATFORM_ERROR,
                     "Mir: Unsupported function %s", __PRETTY_FUNCTION__);