Writing .fc files without any mistake is quite hard. Sometimes a regular
expression pattern compiles fine but it does not match what is intended.
Add a script that detects some issues in .fc files. When this script is
used directly ("./testing/check_fc_files.py"), it checks the content of
policy/. The path to policy/ can also be provided by option -p.
Signed-off-by: Nicolas Iooss <nicolas.iooss@m4x.org>