d: add the custom error message feature

Parser.Context class returns a const YYLocation, so Lexer's method
yyerror() needs to receive the location as a const parameter.

Internal error reporting flow is changed to be similar to that of
the other skeletons. Before, case YYERRLAB was calling yyerror()
with the result of yysyntax_error() as the string parameter. As the
custom error message lets the user decide if they want to use
yyerror() or not, this flow needed to be changed. Now, case YYERRLAB
calls yyreportSyntaxError(), that builds the error message using
yysyntaxErrorArguments(). Then yyreportSyntaxError() passes the
error message to the user defined syntax_error() in case of a custom
message, or to yyerror() otherwise.

In the tests in tests/calc.at, the order of the tokens needs to be
changed in order of precedence, so that the D program outputs the
expected tokens in the same order as the other parsers.

* data/skeletons/lalr1.d: Add the custom error message feature.
* doc/bison.texi: Document it.
* examples/d/calc/calc.y: Adjust.
* tests/calc.at, tests/local.at: Test it.

examples/d/calc/calc.y

@@ -101,7 +101,7 @@ if (isInputRange!R && is(ElementType!R : dchar))
   // Should be a local in main, shared with %parse-param.
   int exit_status = 0;
 
-  void yyerror(YYLocation loc, string s)
+  void yyerror(const YYLocation loc, string s)
   {
     exit_status = 1;
     stderr.writeln(loc.toString(), ": ", s);