time: Use a function instead of properties to retrieve the system date and time locale info

This allows applications to re-query the values if the system locale is changed during runtime, and better matches the other locale functions. A note is included in the documentation mentioning that this can be slow, as it has to call into OS functions.

Also allows for the removal of the init/quit time functions, as they are no longer needed.

src/SDL.c

@@ -53,7 +53,6 @@
 #define SDL_INIT_EVERYTHING ~0U
 
 /* Initialization/Cleanup routines */
-#include "time/SDL_time_c.h"
 #include "timer/SDL_timer_c.h"
 #ifdef SDL_VIDEO_DRIVER_WINDOWS
 extern int SDL_HelperWindowCreate(void);
@@ -210,7 +209,6 @@ int SDL_InitSubSystem(Uint32 flags)
     }
 #endif
 
-    SDL_InitTime();
     SDL_InitTicks();
 
     /* Initialize the event subsystem */
@@ -543,7 +541,6 @@ void SDL_Quit(void)
     SDL_QuitSubSystem(SDL_INIT_EVERYTHING);
 
     SDL_QuitTicks();
-    SDL_QuitTime();
 
 #ifdef SDL_USE_LIBDBUS
     SDL_DBus_Quit();