main: Consistently call SDL_SetMainReady() from SDL_RunApp()

`SDL_SetMainReady()` is not a hard requirement on most platforms, but
calling it sets up the main thread ID and thus has implications for
`SDL_IsMainThread()` for apps that don't use the video subsystem.

Author: castholm

src/main/SDL_runapp.c

@@ -35,6 +35,7 @@ int SDL_RunApp(int argc, char *argv[], SDL_main_func mainFunction, void * reserv
         argv = fallbackargv;
     }
 
+    SDL_SetMainReady();
     return mainFunction(argc, argv);
 }
 

src/main/emscripten/SDL_sysmain_runapp.c

@@ -62,6 +62,7 @@ int SDL_RunApp(int argc, char *argv[], SDL_main_func mainFunction, void * reserv
         }
     }, SDL_setenv_unsafe);
 
+    SDL_SetMainReady();
     return mainFunction(argc, argv);
 }
 

src/main/ps2/SDL_sysmain_runapp.c

@@ -68,7 +68,7 @@ int SDL_RunApp(int argc, char *argv[], SDL_main_func mainFunction, void * reserv
 {
     char fallbackargv0[] = { 'S', 'D', 'L', '_', 'a', 'p', 'p', '\0' };
     char *fallbackargv[2] = { fallbackargv0, NULL };
-    int res;
+    int result;
     (void)reserved;
 
     if (!argv || argc < 0) {
@@ -80,12 +80,11 @@ int SDL_RunApp(int argc, char *argv[], SDL_main_func mainFunction, void * reserv
     init_drivers();
 
     SDL_SetMainReady();
-
-    res = mainFunction(argc, argv);
+    result = mainFunction(argc, argv);
 
     deinit_drivers();
 
-    return res;
+    return result;
 }
 
 #endif // SDL_PLATFORM_PS2

src/main/psp/SDL_sysmain_runapp.c

@@ -83,7 +83,6 @@ int SDL_RunApp(int argc, char *argv[], SDL_main_func mainFunction, void * reserv
     sdl_psp_setup_callbacks();
 
     SDL_SetMainReady();
-
     return mainFunction(argc, argv);
 }
 

src/main/windows/SDL_sysmain_runapp.c

@@ -43,6 +43,8 @@ int SDL_RunApp(int caller_argc, char *caller_argv[], SDL_main_func mainFunction,
     int result;
     (void)reserved;
 
+    SDL_SetMainReady();
+
     // If the provided argv is valid, we pass it to the main function as-is, since it's probably what the user wants.
     // Otherwise, we take a NULL argv as an instruction for SDL to parse the command line into an argv.
     // On Windows, when SDL provides the main entry point, argv is always NULL.