libfltk1.1-dbg 1.1.10-22 (amd64 binary) in ubuntu xenial

 This package is useful to provide a backtrace with symbol names in a
 debugger; this facilitates interpretation of core dumps, and aids in finding
 logic errors in programs using the libraries (or in the libraries themselves).
 .
 Non-programmers will likely have little use for this.
 .
 The Fast Light Toolkit (FLTK) is a cross-platform graphical user interface
 toolkit originally based on libForms.