Use LCLR algorithm for eliminating left-recursion, with lambda terms in SISR for getting trees right.

src/GF/JavaScript/ParJS.y

@@ -122,6 +122,7 @@ Expr16 : Ident { EVar $1 }
   | 'null' { ENull }
   | 'this' { EThis }
   | 'function' '(' ListIdent ')' '{' ListStmt '}' { EFun $3 (reverse $6) }
+  | '(' Expr ',' ListExpr ')' { eseq1_ $2 $4 }
   | '(' Expr ')' { $2 }
 
 
@@ -201,5 +202,6 @@ happyError ts =
     _ -> " before " ++ unwords (map prToken (take 4 ts))
 
 myLexer = tokens
+eseq1_ x_ xs_ = ESeq (x_ : xs_)
 }