Fixed some possible malloc(0) calls reported by static analysis.

SDLMain.m: replace CPS* stuff with activateIgnoringOtherApps (bug #4114)

CPS stuff are deprecated and emit warnings at runtime, e.g.:

warning: CPSGetCurrentProcess(): This call is deprecated and should not be called anymore
warning: CPSSetForegroundOperationState() (as above)
warning: capture_display; Captured mirror master 0x350000c1 (unit 1) on behalf of slave 0x042716c0 (unit 0)

http://lists.libsdl.org/pipermail/sdl-libsdl.org/2006-April/055749.html
suggests doing something like:

ProcessSerialNumber psn = { 0, kCurrentProcess};
TransformProcessType (&psn, kProcessTransformToForegroundApplication);
SetFrontProcess (&psn);

And SetFrontProcess() is deprecated in 10.9. Processes.h suggests
[[NSApplication sharedApplication] activateIgnoringOtherApps: YES]
to make one's own application frontmost.

Use a blank cursor instead of PointerIcon.TYPE_NULL since that shows the default cursor on Samsung DeX

Added support for external mouse in Samsung DeX mode
relative mode doesn't work, but absolute coordinates are functional

Make certain we only hide system UI when we're fullscreen for real. (thanks Rachel!)

Deal with situations where the system UI is shown when the keyboard pops up (thanks Rachel!)

Fixed race condition where Android touch events could get scaled by a render target's viewport

Fixed bug 4094 - No SDL_TEXTEDITING after pressing Alt key on Raspberry Pi Linux

This was reproducible by running an SDL app on the console from an ssh login. In this case the terminal wasn't owned by the user running the app, so we were using the default keymap, which didn't have state transitions defined for ctrl and alt, so once we entered that state keypresses would no longer transition out of that state, nor would they generate text.

As a workaround, we'll just reset to the default shift state if that happens, which means we'll get text for keys pressed while ctrl is held down, but I don't think that's a big problem.

Note that in this case we also can't mute the keyboard, so the keypresses go to the console, which probably isn't what you want...

SDL Android fullscreen code extensively tested on Steam Link with no issues reported

use the 'aborts' pragma of Watcom for SDL_NORETURN functions
SDL_ExitProcess(), SDL_AbortAssertion() and SDLTest_BailOut().

(Commit c8b4a5166613 for bug #4100 removed SDL_NORETURN from
SDL_ExitProcess() and SDL_AbortAssertion() in order to avoid
warnings from windows builds, but that's temporary I guess..)