Fixed typo in header file documentation comment.
diff --git a/include/SDL_joystick.h b/include/SDL_joystick.h
index b0b1c66..f26bb92 100644
--- a/include/SDL_joystick.h
+++ b/include/SDL_joystick.h
@@ -87,7 +87,7 @@ extern DECLSPEC const char *SDLCALL SDL_JoystickNameForIndex(int device_index);
/**
* Open a joystick for use.
- * The index passed as an argument refers tothe N'th joystick on the system.
+ * The index passed as an argument refers to the N'th joystick on the system.
* This index is the value which will identify this joystick in future joystick
* events.
*