Fixed comments in joystick implementation files claiming to be headers.

It seems comments were originally copied from SDL_sysjoystick.h.

src/joystick/dummy/SDL_sysjoystick.c

@@ -22,7 +22,7 @@
 
 #if defined(SDL_JOYSTICK_DUMMY) || defined(SDL_JOYSTICK_DISABLED)
 
-/* This is the system specific header for the SDL joystick API */
+/* This is the dummy implementation of the SDL joystick API */
 
 #include "SDL_joystick.h"
 #include "../SDL_sysjoystick.h"

src/joystick/haiku/SDL_haikujoystick.cc

@@ -22,7 +22,7 @@
 
 #ifdef SDL_JOYSTICK_HAIKU
 
-/* This is the system specific header for the SDL joystick API */
+/* This is the Haiku implementation of the SDL joystick API */
 
 #include <os/support/String.h>
 #include <os/device/Joystick.h>

src/joystick/iphoneos/SDL_sysjoystick.m

@@ -20,7 +20,7 @@
 */
 #include "../../SDL_internal.h"
 
-/* This is the system specific header for the SDL joystick API */
+/* This is the iOS implementation of the SDL joystick API */
 
 #include "SDL_joystick.h"
 #include "../SDL_sysjoystick.h"

src/joystick/linux/SDL_sysjoystick.c

@@ -26,7 +26,7 @@
 #error SDL now requires a Linux 2.4+ kernel with /dev/input/event support.
 #endif
 
-/* This is the system specific header for the SDL joystick API */
+/* This is the Linux implementation of the SDL joystick API */
 
 #include <sys/stat.h>
 #include <unistd.h>

src/joystick/psp/SDL_sysjoystick.c

@@ -19,7 +19,7 @@
   3. This notice may not be removed or altered from any source distribution.
 */
 
-/* This is the system specific header for the SDL joystick API */
+/* This is the PSP implementation of the SDL joystick API */
 #include <pspctrl.h>
 #include <pspkernel.h>