Avoid unnecessary calls to sqlite3BtreeEnterAll() and sqlite3BtreeLeaveAll()
when no btree is using shared-cache.

FossilOrigin-Name: cfb3158204628eb2fd170090a7f212df0e4ce6c9
diff --git a/src/sqliteInt.h b/src/sqliteInt.h
index d78d207..6a01029 100644
--- a/src/sqliteInt.h
+++ b/src/sqliteInt.h
@@ -1296,6 +1296,7 @@
   u8 vtabOnConflict;            /* Value to return for s3_vtab_on_conflict() */
   u8 isTransactionSavepoint;    /* True if the outermost savepoint is a TS */
   u8 mTrace;                    /* zero or more SQLITE_TRACE flags */
+  u8 skipBtreeMutex;            /* True if no shared-cache backends */
   int nextPagesize;             /* Pagesize after VACUUM if >0 */
   u32 magic;                    /* Magic number for detect library misuse */
   int nChange;                  /* Value returned by sqlite3_changes() */