add database open with VSF virtual file system

src/fmdb/FMDatabase.h

@@ -219,6 +219,7 @@ typedef int(^FMDBExecuteStatementsCallbackBlock)(NSDictionary *resultsDictionary
 
 #if SQLITE_VERSION_NUMBER >= 3005000
 - (BOOL)openWithFlags:(int)flags;
+- (BOOL)openWithFlags:(int)flags andVFS:(const char*)vfs;
 #endif
 
 /** Closing a database connection

src/fmdb/FMDatabase.m

@@ -151,11 +151,14 @@ - (BOOL)open {
 
 #if SQLITE_VERSION_NUMBER >= 3005000
 - (BOOL)openWithFlags:(int)flags {
+    return [self openWithFlags:flags andVFS:NULL];
+}
+- (BOOL)openWithFlags:(int)flags andVFS:(const char*)vfs {
     if (_db) {
         return YES;
     }
 
-    int err = sqlite3_open_v2([self sqlitePath], &_db, flags, NULL /* Name of VFS module to use */);
+    int err = sqlite3_open_v2([self sqlitePath], &_db, flags, vfs);
     if(err != SQLITE_OK) {
         NSLog(@"error opening!: %d", err);
         return NO;