Skip changes to function *types* in the leaf reporter
    
    In the leaf reporter, it doesn't make sense to report changes about
    function types, as function types are a concept that is internal-only
    to Libabigail.
    
    	* src/abg-leaf-reporter.cc
    	(leaf_reporter::report_changes_from_diff_maps): Don't report
    	function type changes.
    
    Signed-off-by: Dodji Seketeli <dodji@redhat.com>