[feature] Add parsing support for rename expression

Author: gabriele-tomassetti

exist-core/src/main/antlr/org/exist/xquery/parser/XQuery.g

@@ -724,7 +724,8 @@ exprSingle throws XPathException
 	| ( "insert" ( "node" | "nodes" ) ) => xqufInsertExpr
 	| ( "delete" ( "node" | "nodes" ) ) => xqufDeleteExpr
 	| ( "replace" ( "value" | "node" ) ) => xqufReplaceExpr
-	| ( "copy" DOLLAR) => copyModifyExpr
+	| ( "rename" "node" ) => xqufRenameExpr
+	| ( "copy" DOLLAR ) => copyModifyExpr
 	| ( "invoke" "updating" ) => dynamicUpdFunCall
 	| orExpr
 	;
@@ -800,6 +801,11 @@ xqufReplaceExpr throws XPathException
 	"replace"^ ("value" "of"!)? "node"! exprSingle "with"! exprSingle
 	;
 
+xqufRenameExpr throws XPathException
+:
+	"rename"^ "node"! exprSingle "as"! exprSingle
+	;
+
 copyModifyExpr throws XPathException
 :
 	"copy"^ letVarBinding ( COMMA! letVarBinding )*