See the complaint on #4039. This doesn't fix that particular
issue (it's somewhat unrelated), but does solve around
a file parsing problem reported by @void-in
This commit changes how os_name and os_flavor are handled
for client-side exploits, matching recent changes to the
server-side exploits and scanner fingerprints.
This commit also updates the client-side fingerprinting to
take into account Windows 8.1 and IE 9, 10, and 11.