Add an experimental busy_timeout pragma to facilitate access to the

sqlite3_busy_timeout() interfaces for programmers that are working from
behind a language wrapper that does not expose that interface.

FossilOrigin-Name: 22ebc668516bc3dd5782d6d3d42dc7fd2eed7d79

src/main.c

@@ -1156,6 +1156,7 @@ int sqlite3_busy_timeout(sqlite3 *db, int ms){
     db->busyTimeout = ms;
     sqlite3_busy_handler(db, sqliteDefaultBusyCallback, (void*)db);
   }else{
+    db->busyTimeout = 0;
     sqlite3_busy_handler(db, 0, 0);
   }
   return SQLITE_OK;