c++: minor changes

* data/lalr1.cc: Fix oldish comment.
* data/stack.hh: Prefer typename for type names.
Use size() instead of duplicating it.
* examples/variant-11.yy, examples/variant.yy (yylex): Use int,
as this is the type of the semantic value.

examples/variant.yy

@@ -114,9 +114,10 @@ namespace yy
   parser::symbol_type
   yylex ()
   {
-    static int stage = -1;
-    ++stage;
-    parser::location_type loc (nullptr, stage + 1, stage + 1);
+    static int count = 0;
+    const int stage = count;
+    ++count;
+    parser::location_type loc (nullptr, unsigned (stage + 1), unsigned (stage + 1));
     switch (stage)
       {
       case 0: