Fix Mac builds

- [Mac] Update to QT 5 (5.9.1)
- [Mac] Update to SDL 2 (2.0.5)
- [Mac] Update to Gettext 0.19.8.1
- [Mac] Update to GLEW 1.13.0
- [Mac] Update to LibOgg 1.3.2
- [Mac] Update to LibPng 1.6.32
- [Mac] Update to LibVorbis 1.3.5
- [Mac] Remove FontConfig
- [Mac] Remove Fribidi
- [Mac] Remove Prebuilt FreeType
- [Mac] Remove QuesoGLC
- [Mac] Add FreeType 2.8
- [Mac] Add Harfbuzz 1.4.8
- [Mac] Enhance fetch scripts to support fetching (and unpacking) DMG files (currently used for: SDL 2)
- [Mac] Enhance fetch scripts to use SHA256
- [Mac] Add patch scripts for transforming QT5 frameworks to support Xcode's built-in code signing
- [Mac] Fix the Help generator script
- [Mac] Fix the Gettext script
- [Mac] Fix the Xcode project to reflect the current Warzone sources (and the above dependencies)
- [Mac] Enable ARC for the main WZ sources Objective-C code
- [Mac] Enable more build warnings
- [Mac] Overhaul the way the SDL Mac app is run (see: WZSDLAppDelegate)
- [Mac] Properly handle NSApplication termination by posting an SDL_QUIT event and allowing the main game loop to handle saving and shutting down gracefully
- [Mac] Remove / replace some deprecated APIs and frameworks
- [Mac] Remove extra (and outdated) Mac-specific copies of the COPYING files - use the main ones instead
- [Mac] Add various useful command-line options to the main app Xcode build scheme (disabled by default)
- [Mac] Add sandboxing support (requires code signing to be configured)
- [Mac] Add macosx/README.md with detailed build instructions