Add the experimental SQLITE_FCNTL_JOURNAL_POINTER file control for obtaining

the sqlite3_file pointer associated with a rollback journal or WAL file.

FossilOrigin-Name: a02ace9a746ff02fc1a5969bf13939b568624f93

src/wal.c

@@ -3310,4 +3310,10 @@ int sqlite3WalFramesize(Wal *pWal){
 }
 #endif
 
+/* Return the sqlite3_file object for the WAL file
+*/
+sqlite3_file *sqlite3WalFile(Wal *pWal){
+  return pWal->pWalFd;
+}
+
 #endif /* #ifndef SQLITE_OMIT_WAL */