LWP::UserAgent WWW-Authenticate header regular expression does not match RFC

All,

I noticed the "scheme" regular expression in LWP::UserAgent used to 
match the authentication scheme sent in a WWW-Authenticate header does 
not match the RFC's list of allowed characters for this field.

RFC2617 uses the type "token" from RFC2616, which includes several 
characters not present in the "scheme" regular expression on line 344 of 
UserAgent.pm. I believe this regular expression should be expanded to 
allow the missing characters (which is quite a large list, but namely 
missing "." and "_").

It's only a one-line change, so I'm not sure if you'd prefer I submit a 
patch or just report the issue directly.

Thanks,
John