Bug fix to ensure that a User-Agent string can be specified when the
fwknop client uses wget via SSL to resolve the external IP address. This
closes issue #134 on github reported by Barry Allard. The fwknop now
uses the wget '-U' option to specify the User-Agent string with a
default of "Fwknop/<version>". In addition, a new command line argument
"--use-wget-user-agent" to allow the default wget User-Agent string to
apply instead.
External IP resolution via '-R' (or '--resolve-ip-http') is now done via SSL by
default. The IP resolution URL is now 'https://www.cipherdyne.org/cgi-gin/myip',
and a warning is generated in '-R' mode whenever a non-HTTPS URL is specified
(it is safer just to use the default). The fwknop client leverages 'wget' for
this operation since that is cleaner than having fwknop link against an SSL
library.
