Fix vbsp missing skybox error case when building cubemaps.

The code previoused checked the address of a stack array that would always
evaluate non-zero, which wasn't what was intended.
Fix SortEntry operator< not being const.

This solves a problem where the standard library expects it to be const,
which causes compilation problems on GNU/Linux.
Fix bad class declaration in utils/vbsp/ivp.

The duplicated namespace in the member declaration causes the class to not
compile using gcc.
Fix use of temporary vector in utils/vrad/vraddetailprops.cpp.

This fixes a gcc compile error.
Avoid conflict with gamma(3) in utils/vrad/vrad.h.

The name of the global variable conflicts with the deprecated gamma function
from <math.h> on some systems. Additionally the variable appears to be
unused - should it rather just be deleted from the codebase?
Use Q_strncpy in utils/vbsp/detailobjects.cpp.
Fix bsp lump names being declared non-portably.

gcc issues warnings when encountering multicharacter constants, so we'll
simply emulate them in a manner works portably. The code assumes we are
using a little-endian machine - the real solution would be using using four
chars instead of an enum.
General:
* Fixed a variety of server browser issues with mods based on this SDK
* Fixed many warnings on various platforms
* Added source code for fgdlib and raytrace
* Updated many source files with the latest shared source from TF2.

OSX:
* Added support for Xcode 4.6
* Switched OSX builds to use Xcode instead of makefiles
* Moved libs from src/lib/osx32 to src/lib/public/osx32 or src/lib/common/osx32 to match windows better.

Linux:
* Moved libs from src/lib/linux32 to src/lib/public/linux32 or src/lib/common/linux32 to match windows better.
Merge commit '82fe37f'
* Fixed Source Mod back-compatability by reordering methods in a couple interfaces.
* Added missing singleplayer OSX libs
* Updated vpc and libs.
Merge branch 'master' of https://github.com/ValveSoftware/source-sdk-2013