EmulatorPkg:Unix: Add support for X11 on Mac OS X via XQuartz

EmulatorPkg:Unix: Add support for X11 on Mac OS X via XQuartz

Starting in OS X Mountain Lion X11 is not longer part of the OS install, so
you must download it from http://xquartz.macosforge.org.
To make XQuartz work with the EmulatorPkg an include path needs to be added.
The build tools fail the build if you try to add an absolute inculde path to
the X11 headers, so Unix/Host/X11IncludeHack, a symbolic link, was added to
get the system building.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Anderw Fish <afish@apple.com>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@15929 6f19259b-4bc3-4df7-8a09-765794883524