Update XFileSharingPro.py

fixed XFileSharingPro to work with xvidstage.com

I changed re.S into re.DOTALL for readability and, if I understand correctly, then DOTALL doesn't have any effect at all without MULTILINE. 
Second, it seemed kind of arbitrary to require "Enter code" to be in bold.
In any case, both changes are necessary for xvidstage to work - I verified that it does work with these changes.