[X] Add zlib dependency
[X] Support for HP-UX
    Fixed upstream (Issue #937).
[X] Support for AIX
    Fixed upstream (Issue #942).
[X] Support for NetBSD
    Fixed upstream (Issue #944).
[ ] Static libraries should not be installed with execute permissions
    "fltk.list" has entires with 444 permissions, looks like a bug.
[ ] Check for library suffixes on AIX, HP-UX and macOS
    Should use libtool like FLTK 1.3
[X] Build test programs only on request (make test)
    This was rejected upstream (Issue #940).
    Disable build of test programs with new option "--disable-test".
[X] Fix X11 options
[X] Add cairo and wayland options
