Initial maemo platform support

Adds Nokia N900, N810 and N800 support.

Features:
- Introduce maemo specific platform defines
- Play audio in silent mode
- Stop playback on incoming calls
- Battery level readout
- Bluetooth headset support
- Save CPU by disabling screen updates if the display
  is off or the app doesn't have input focus
- N900: GStreamer audio backend

Kudos to kugel for the code review.

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@29248 a1c6a512-1295-4272-9138-f99709370657

apps/misc.c

@@ -526,7 +526,7 @@ static void unplug_change(bool inserted)
 
 long default_event_handler_ex(long event, void (*callback)(void *), void *parameter)
 {
-#if CONFIG_PLATFORM & PLATFORM_ANDROID
+#if CONFIG_PLATFORM & (PLATFORM_ANDROID|PLATFORM_MAEMO)
     static bool resume = false;
 #endif
 
@@ -619,7 +619,7 @@ long default_event_handler_ex(long event, void (*callback)(void *), void *parame
             iap_handlepkt();
             return SYS_IAP_HANDLEPKT;
 #endif
-#if CONFIG_PLATFORM & PLATFORM_ANDROID
+#if CONFIG_PLATFORM & (PLATFORM_ANDROID|PLATFORM_MAEMO)
         /* stop playback if we receive a call */
         case SYS_CALL_INCOMING:
             resume = audio_status() == AUDIO_STATUS_PLAY;