- it's no longer necessary to take care of the change in the layout of "struct libdecor"
between versions ≤ 0.2.2 and > 0.2.2 of libdecor
- version > 0.2.2 contains MR131, that is, it defines LIBDECOR_WINDOW_STATE_RESIZING
so the hack to emulate it is no longer necessary
- CMake option FLTK_USE_SYSTEM_LIBDECOR now requires libdecor version > 0.2.2
to be activated, otherwise the bundled libdecor is used
- what will be the libdecor version after 0.2.2 (0.2.3? 0.3.0?) is not known as of today
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