Overlay: Add Direct3D 11 support

* Based on an initial patch by Benjamin Jemlich
* Effects11 code based on changes by nyet
Merge pull request #1082 from mumble-voip/olay-11

Overlay: Add Direct3D 11 support
scripts/release.pl: add vpath special-case for fx11.
plugins/borderlands2: fix version check.
plugins/borderlands2: add support for v1.7.0.
OSInfo: use full Windows version when version string is user-facing.

This adds a new method, OSInfo::getOSDisplayableVersion(),
which returns a version string that is suitable for displaying
to regular users.

Furthermore, Mumble's User Information dialog and Murmur have been
modified to use this new method when displaying OS version strings
to users.

On Windows, the new method returns the full product version of the
OS, such as "Windows 8 Pro" (as opposed to 6.2.9200, which is the
equivalent result of the getOSVersion() method).

There are places in Mumble where the original "simple" version
string is required for compatibility or aesthetic reasons, such
as statistics and Mumble's HTTP user agent. Those places keep
the older version (by keeping their calls to the original
getOSVersion() instead of switching to the "displayable" variant).

It might seem overkill to jump through hoops to be able to show the
full product version, but it can be helpful for, say, server admins
to have access to the full product version if they need to
troubleshoot issues with their users.
mumble.appcompat.manifest: add Windows 8 and Windows 8.1 entries.

Among other things, this allows OSInfo to produce correct version
strings on Windows 8.1.
OSInfo: fix display of Windows service packs in getOSDisplayableVersion.

I botched this when I did a few fix-ups while merging.
MainWindow: add Cancel button to the "Minimize or Close?" message box.
Messages: use actual username (instead of the ConnectDialog username) in msgPermissionDenied.
scripts/release.pl: remove slicer-specific deployment functionality.

Nobody is using release.pl for deploying tarballs
automatically anymore.

Our builder bots were manually sed'ing out these
parts of the code before running release.pl, so by
dropping it completely, we can clean up their build
scripts a bit.