Removed SDL_HasGamepads(), SDL_HasJoysticks(), and SDL_HasSensors()

Also cleaned up logic for whether we need to poll for events:
- We need to periodically poll for joysticks to handle hotplug.
- We need to frequently poll for joysticks and sensors when they're open so their state can be updated

src/joystick/SDL_gamepad.c

@@ -1914,23 +1914,6 @@ int SDL_InitGamepads(void)
     return 0;
 }
 
-SDL_bool SDL_HasGamepads(void)
-{
-    SDL_bool retval = SDL_FALSE;
-    SDL_JoystickID *joysticks = SDL_GetJoysticks(NULL);
-    if (joysticks) {
-        int i;
-        for (i = 0; joysticks[i]; ++i) {
-            if (SDL_IsGamepad(joysticks[i])) {
-                retval = SDL_TRUE;
-                break;
-            }
-        }
-        SDL_free(joysticks);
-    }
-    return retval;
-}
-
 SDL_JoystickID *SDL_GetGamepads(int *count)
 {
     int num_joysticks = 0;

src/joystick/SDL_joystick.c

@@ -332,19 +332,21 @@ int SDL_InitJoysticks(void)
     return status;
 }
 
-SDL_bool SDL_HasJoysticks(void)
+SDL_bool SDL_JoysticksOpened(void)
 {
-    int i;
-    SDL_bool retval = SDL_FALSE;
+    SDL_bool opened;
+
     SDL_LockJoysticks();
-    for (i = 0; i < SDL_arraysize(SDL_joystick_drivers); ++i) {
-        if (SDL_joystick_drivers[i]->GetCount() > 0) {
-            retval = SDL_TRUE;
-            break;
+    {
+        if (SDL_joysticks != NULL) {
+            opened = SDL_TRUE;
+        } else {
+            opened = SDL_FALSE;
         }
     }
     SDL_UnlockJoysticks();
-    return retval;
+
+    return opened;
 }
 
 SDL_JoystickID *SDL_GetJoysticks(int *count)

src/joystick/SDL_joystick_c.h

@@ -49,6 +49,9 @@ extern SDL_bool SDL_JoysticksLocked(void);
 /* Make sure we currently have the joysticks locked */
 extern void SDL_AssertJoysticksLocked(void) SDL_ASSERT_CAPABILITY(SDL_joystick_lock);
 
+/* Function to return whether there are any joysticks opened by the application */
+extern SDL_bool SDL_JoysticksOpened(void);
+
 /* Function to get the next available joystick instance ID */
 extern SDL_JoystickID SDL_GetNextJoystickInstanceID(void);