Update query operation enum and add EXECUTE

Changed the query operation enum to contain implicit enum values instead
of providing. The operation was never used as a bitmask so it is pointless
to declare them as such.

Added the EXECUTE type to the enum and used it in qc_sqlite and
qc_mysqlembedded.

query_classifier/qc_sqlite/qc_sqlite.c

@@ -2032,6 +2032,7 @@ void maxscaleExecute(Parse* pParse, Token* pName)
 
     info->status = QC_QUERY_PARSED;
     info->type_mask = QUERY_TYPE_WRITE;
+    info->operation = QUERY_OP_EXECUTE;
 
     // If information is collected in several passes, then we may
     // this information already.