Update SDL2 to the latest hg revision of 2.0.4.

libs/SDL2/include/SDL_joystick.h

@@ -71,6 +71,16 @@ typedef struct {
 
 typedef Sint32 SDL_JoystickID;
 
+typedef enum
+{
+    SDL_JOYSTICK_POWER_UNKNOWN = -1,
+    SDL_JOYSTICK_POWER_EMPTY,
+    SDL_JOYSTICK_POWER_LOW,
+    SDL_JOYSTICK_POWER_MEDIUM,
+    SDL_JOYSTICK_POWER_FULL,
+    SDL_JOYSTICK_POWER_WIRED,
+    SDL_JOYSTICK_POWER_MAX
+} SDL_JoystickPowerLevel;
 
 /* Function prototypes */
 /**
@@ -96,6 +106,11 @@ extern DECLSPEC const char *SDLCALL SDL_JoystickNameForIndex(int device_index);
  */
 extern DECLSPEC SDL_Joystick *SDLCALL SDL_JoystickOpen(int device_index);
 
+/**
+ * Return the SDL_Joystick associated with an instance id.
+ */
+extern DECLSPEC SDL_Joystick *SDLCALL SDL_JoystickFromInstanceID(SDL_JoystickID joyid);
+
 /**
  *  Return the name for this currently opened joystick.
  *  If no name can be found, this function returns NULL.
@@ -242,6 +257,10 @@ extern DECLSPEC Uint8 SDLCALL SDL_JoystickGetButton(SDL_Joystick * joystick,
  */
 extern DECLSPEC void SDLCALL SDL_JoystickClose(SDL_Joystick * joystick);
 
+/**
+ *  Return the battery level of this joystick
+ */
+extern DECLSPEC SDL_JoystickPowerLevel SDLCALL SDL_JoystickCurrentPowerLevel(SDL_Joystick * joystick);
 
 /* Ends C function definitions when using C++ */
 #ifdef __cplusplus