Critical compilation fix for windows not using GLFW. Android and iOS won't compile.

Fixes #2894 which breaks iOS / Android in my tests.

iOS Build error:
ofAppGLFWWindow.h : Line 10.
```openFrameworks/libs/openFrameworks/app/ofAppGLFWWindow.h:10:10: 'GLFW/glfw3.h' file not found```

Android throws error a bouts glfw.

Problem caused by:
https://github.com/openframeworks/openFrameworks/blob/master/libs/openFrameworks/events/ofEvents.cpp#L6
And 
https://github.com/openframeworks/openFrameworks/blob/master/libs/openFrameworks/events/ofEvents.cpp#L219-225

-Wrapped functions that are related to GLFW in the preprocessor defined
in it when used for ofEvents.cpp