Windows - fix proxy types for manually specified proxies

Windows - fix proxy types for manually specified proxies

When the windows internet options are used to specify a
different proxy for each protocol, assume the proxy server type
matches that protocol too.
e.g. "socks=qt-test-server:1080" is both tagged for socks, and
assumed to be a socks server.
"ftp=qt-test-server:2121" is assumed to be an ftp proxy
"ftp=http://qt-test-server:3128" is overridden to be a http proxy
used for ftp.

Task-number: QTBUG-10502
Change-Id: I70615c89d6ede53f0e7d62e6d0754b90d042aa2e
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>