reconcile '[]' and [] (#644), solve remaining conformity issues (#648), move (-->) from dcgs.pl to builtins.pl (#649)

src/lib/builtins.pl

@@ -24,6 +24,8 @@ user:term_expansion((:- op(Pred, Spec, [Op | OtherOps])), OpResults) :-
 :- op(400, yfx, [div, //, rdiv, <<, >>, mod, rem]).
 :- op(200, fy, [+, -, \]).
 
+:- op(1200, xfx, -->).
+
 % arithmetic comparison operators.
 :- op(700, xfx, [>, <, =\=, =:=, >=, =<]).
 

src/lib/dcgs.pl

@@ -1,7 +1,7 @@
-:- module(dcgs, [op(1200, xfx, -->),
-		 op(1105, xfy, '|'),
-		 phrase/2,
-		 phrase/3]).
+:- module(dcgs,
+          [op(1105, xfy, '|'),
+		   phrase/2,
+		   phrase/3]).
 
 :- use_module(library(error)).
 :- use_module(library(lists), [append/3]).