Corrected eglext.h path.

src/egl_platform.h

@@ -36,7 +36,7 @@
 // This path may need to be changed if you build GLFW using your own setup
 // We ship and use our own copy of eglext.h since GLFW uses fairly new
 // extensions and not all operating systems come with an up-to-date version
-#include "../support/GL/eglext.h"
+#include "../support/EGL/eglext.h"
 
 // Do we have support for dlopen/dlsym?
 #if defined(_GLFW_HAS_DLOPEN)