The functions to show/hide/toggle the on-screen keyboard have been folded into the text input state.
Calling SDL_StartTextInput() will automatically show the on-screen keyboard if it's available.
Calling SDL_StopTextInput() will automatically hide the on-screen keyboard if it's available.
There is a new API function SDL_IsTextInputActive() which will return whether text input is currently active.
Text input is disabled by default, you must call SDL_StartTextInput() when you are ready to accept text input.
SDL_HasScreenKeyboardSupport() no longer needs to be passed a window.
The iPhone-specific on-screen keyboard functions have been removed.
