Add SDL2 and related libraries
Some SDL2 updates

Used provide Xcode projects as template, based off SDL2 rc1, SDL2_image rc1 and SDL2_gfx r5
Update SDL2 and SDL2_image for 2.0.0 final releases
SDL2 2.0.1
Add target to build WebP

Add WebP target so that it can be code signed, and therefore so can SDL2_image. Deployment target is now 10.5 for all targets, as SDL2 cannot be built for earlier systems.
Bullet 2.82

Also move all four bullet components to one folder, so the source only needs to exist once.
cURL 7.33.0