Add shared app gid to fs config

This will allow native tools to be able to know where the shared app
gids start and end.

Change-Id: Ie4529baf36b361c51c42f079b259c352e316647f
diff --git a/include/private/android_filesystem_config.h b/include/private/android_filesystem_config.h
index 6521cbe..33ecd9a 100644
--- a/include/private/android_filesystem_config.h
+++ b/include/private/android_filesystem_config.h
@@ -87,6 +87,9 @@
 
 #define AID_USER        100000  /* offset for uid ranges for each user */
 
+#define AID_SHARED_GID_START 50000 /* start of gids for apps in each user to share */
+#define AID_SHARED_GID_END   59999 /* start of gids for apps in each user to share */
+
 #if !defined(EXCLUDE_FS_CONFIG_STRUCTURES)
 struct android_id_info {
     const char *name;