The joystick subsystem has complex precedence logic to deal multiple competing
backends like XInput, RawInput, and WGI. Let it fire the MaybeAdd callbacks
for joystick devices, since it knows which backend will end up managing them.
This resolves a situation where the RawInput joystick backend would take
control of an XInput device but the XInput haptic backend would still create
a haptic device. Since the XInput joystick backend didn't own the underlying
joystick device, we'd end up with an orphaned haptic device that didn't work
with SDL_HapticOpenFromJoystick() on the associated joystick device.
This allows us to set an explicit stack size (overriding the system default
and the global hint an app might have set), and remove all the macro salsa
for dealing with _beginthreadex and such, as internal threads always set those
to NULL anyhow.
I've taken some guesses on reasonable (and tiny!) stack sizes for our
internal threads, but some of these might turn out to be too small in
practice and need an increase. Most of them are simple functions, though.
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().
