When a connection disconnects from a shared-cache database, only delete the in-memory schema if there are no other connections.

FossilOrigin-Name: 46f4eb5430d7bc9a339cdf7124ff4bd518eaa39b
diff --git a/src/sqliteInt.h b/src/sqliteInt.h
index cb178ff..cefff07 100644
--- a/src/sqliteInt.h
+++ b/src/sqliteInt.h
@@ -3101,6 +3101,7 @@
 #  define sqlite3GetVTable(X,Y)  ((VTable*)0)
 #else
    void sqlite3VtabClear(sqlite3 *db, Table*);
+   void sqlite3VtabDisconnect(sqlite3 *db, Table *p);
    int sqlite3VtabSync(sqlite3 *db, char **);
    int sqlite3VtabRollback(sqlite3 *db);
    int sqlite3VtabCommit(sqlite3 *db);