filesystem: expose a special flag for archive mounter to skip included WADs

filesystem/filesystem.c

@@ -315,7 +315,7 @@ searchpath_t *FS_AddArchive_Fullpath( const fs_archive_t *archive, const char *f
 	fs_searchpaths = search;
 
 	// time to add in search list all the wads from this archive
-	if( archive->load_wads )
+	if( archive->load_wads && !FBitSet( flags, FS_SKIP_ARCHIVED_WADS ))
 	{
 		stringlist_t list;
 		int i;

filesystem/filesystem.h

@@ -43,6 +43,8 @@ enum
 	FS_CUSTOM_PATH    = BIT( 3 ), // gamedir but with custom/mod data
 	FS_GAMERODIR_PATH = BIT( 4 ), // gamedir but read-only
 
+	FS_SKIP_ARCHIVED_WADS = BIT( 5 ), // don't mount wads inside archives automatically
+
 	FS_GAMEDIRONLY_SEARCH_FLAGS = FS_GAMEDIR_PATH | FS_CUSTOM_PATH | FS_GAMERODIR_PATH
 };