Posted version 0.99m, macOS version, HW renderer optimizations, minor other stuff

Version 0.99m of Post Apocalyptic Petra adds a new platform: macOS. I have only tested this on macOS 10.13 (High Sierra) which is the latest version that my aging iMac (late 2009 model) supports, but it should work on any 64bit macOS from 10.8 and up. It may even work on the new M1 macs but i have no idea. It does use SDL 1.2 though and it all depends on how nice that library plays with the recent macOS versions.

Here is the full changelog:

• Added macOS version
• Added gamma/brightness adjustment in the software rendering versions with F2/F3
• Added -window parameter for the windows version (meant to be used with the GDI version)
• Optimized triangle batch search for the hardware accelerated versions (should make Direct3D versions work on even older PCs)
• The editor can paste a texture from the clipboard (only for previewing)
• Source changes to make possible using a different data directory (this is preparation for another game i might make with the engine)