ids-functions.pl: Add function to create empty files

ids-functions.pl: Add function to create empty files

This generic function can be used to create any kind of emtpy files -
it just requires the full path and filename to work.

If the specified file exists at calltime, the function will abort
to prevent from overwriting existing files and content.

Signed-off-by: Stefan Schantl <stefan.schantl@ipfire.org>