Virtual package libfltk-dev is provided by:
dpkg-query: no packages found matching libfltk1.1-dev Desired=Unknown/Install/Remove/Purge/Hold | Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend ||/ Name Version Architecture +++-====================-==========-==================================== ii libfltk1.3-dev:amd64 1.3.8-5 amd64 Fast Light Toolkit - development files 1 packages