Control allowed extensions (-f and -F)

Syntax: -fEXT or: -FEXT

The -f option will add EXT to the list of allowed file extensions. The -F option will remove EXT from the list of allowed file extensions. Do not include the '.' in EXT. It is implied. The default list of allowed extensions is:

html  htm  txt

e.g.: ``gw -Ftxt -fshtml'' allows just ".html", ".htm", and ".shtml" files.

-f and -F may be used multiple times as needed to specify multiple extensions.

Note: The pre-version 2 behavior of wiping the entire extension list when no EXT was supplied to -f has been removed.