Eric Wasylishen
The following patch adds Metal.framework to the "link binary with libraries" section of each test program, with "status" set to "optional", which fixes link errors on all of the test programs. I'm not sure if this is a correct fix - the fact that this was necessary might indicate the static SDL2.a library has a hard dependency on Metal.framework (?) - but it gets the test programs working in Xcode again.
It also adds testyuv_cvt.c to the testoverlay2 target, fixing a link error.
The internal function SDL_EGL_LoadLibrary() did not delete and remove a mostly
uninitialized data structure if loading the library first failed. A later try to
use EGL then skipped initialization and assumed it was previously successful
because the data structure now already existed. This led to at least one crash
in the internal function SDL_EGL_ChooseConfig() because a NULL pointer was
dereferenced to make a call to eglBindAPI().
