Unify X11 preprocessor macros

Nicolas Fellarequested to merge
work/x11macros into master

Currently we have three different ones: HAVE_X11, HAVE_XCURSOR, and HAVE_XFIXES

Since we assume that when building with X11 support all X11 libs are present we can unify those into one

Also consistently use cmakedefine01 and remove some now obsolete config headers

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