Adds SDL force feedback support (Thanks, taylor!)

git-svn-id: svn://svn.icculus.org/fs2open@10096 387891d4-d844-0410-90c0-e4c51a9137d3
Removes redundant code


git-svn-id: svn://svn.icculus.org/fs2open@10097 387891d4-d844-0410-90c0-e4c51a9137d3
Adds an SCP_Warning function that acts as frontend to SDL_ShowSimpleMessagebox


git-svn-id: svn://svn.icculus.org/fs2open@10098 387891d4-d844-0410-90c0-e4c51a9137d3
Adds include and linker directories to the FRED project (Does not resolve building errors though!)


git-svn-id: svn://svn.icculus.org/fs2open@10099 387891d4-d844-0410-90c0-e4c51a9137d3
MSVC 2008 Project Updates for SDL2/joy-sdl.

git-svn-id: svn://svn.icculus.org/fs2open@10100 387891d4-d844-0410-90c0-e4c51a9137d3
For now, we need to duplicate this code in osapi.cpp and osapi_unix.cpp, so that Mac and Unix can compile

git-svn-id: svn://svn.icculus.org/fs2open@10101 387891d4-d844-0410-90c0-e4c51a9137d3
Support SDL2 bindings and SDL2.framework on Xcode4/5. Please remember to delete your projects/Xcode4/Frameworks/ folder and recreate from the modified projects/Xcode4/Frameworks.tgz

git-svn-id: svn://svn.icculus.org/fs2open@10102 387891d4-d844-0410-90c0-e4c51a9137d3
Ensure the SDL2.framework is copied into the final application bundle

git-svn-id: svn://svn.icculus.org/fs2open@10103 387891d4-d844-0410-90c0-e4c51a9137d3
SDL2 code changes to bring more common platform code into play

git-svn-id: svn://svn.icculus.org/fs2open@10104 387891d4-d844-0410-90c0-e4c51a9137d3