Diagonal flipping with RenderCopyEx

Ivan Rubinson

As it turns out, it was impossible to render a texture flipped diagonally (both vertically and horizontally) with one RenderCopyEx call.
With help from #SDL @ freenode, we came up with a fix.
Started BeOS removal: merged BeOS thread and pthread code.

Haiku uses most of the standard pthread API, with a few #ifdefs where we
still need to fallback onto the old BeOS APIs.

BeOS, however, does not support pthreads (or maybe doesn't support it well),
so I'm unplugging support for the platform with this changeset. Be Inc went
out of business in 2001.

--HG--
extra : rebase_source : c7227f47193228c898cc997ebcf9bb00ead329e6
Added SDL_DetachThread() API.

--HG--
extra : rebase_source : 0e37621bc7ae79dd3f15030e7131aa774ad8df82
Patched to compile on Haiku.