Pull in the new Havok source package that pulls includes the new Havok Libs package with corrected Win64 libs that are properly built for VS2013

Remove winmmshim 'hack' from project and set volume directly from CEF media plugin using Windows system call.  WinMMShim was only needed for XP systems and since we no longer support XP, it is not required.

The present CMake logic wants to pass FIXED:NO to the linker for 64-bit
builds, which on the face of it seems like a Good Thing: it permits code to be
relocated in memory, preventing collisions if two libraries happen to want to
load into overlapping address ranges.

However the way it's being specified is wrong and harmful. Passing /FIXED:NO
to the compiler command line engages /FI (Forced Include!) of a nonexistent
file XED:NO -- producing lots of baffling fatal compile errors.

Thanks Callum for diagnosing this!

Evidently the LL_VIEWER_CHANNEL macro (defined on the compiler command line)
used to contain enclosing double quotes. Something changed (newer CMake
version?) so that the macro now expands as Second Life Release rather than as
"Second Life Release". That leads to syntax errors when it's used.

Add C++ preprocessor trickery to stringize the value of the macro.

Pull in new version of KDU third party package that is build (correctly) as a static library vs. a stub library/DLL

Specifically, DriverCallback() was accepting several DWORD arguments that
should really be DWORD_PTR arguments. In a 32-bit compile, evidently that was
okay, but for 64 bits they're different sizes.

We never intend to support 32-bit Mac builds any more.

This change eliminates the autobuild warning about not finding darwin64 and
therefore falling back on plain darwin.