skip ignored commands, similar to former proper_command_at (see d68ea01d5084) -- relevant to Output, Query_Operation etc.;
tuned signature;
syntax: glob
*~
*.class
*.jar
*.orig
*.rej
.DS_Store
syntax: regexp
^contrib
^heaps/
^browser_info/
^doc/.*\.dvi
^doc/.*\.eps
^doc/.*\.pdf
^doc/.*\.ps
^src/Tools/jEdit/dist/