lalr1.cc: fix compiler warnings

Reported by Rob Conde.
http://lists.gnu.org/archive/html/bug-bison/2013-03/msg00003.html

* data/stack.hh (operator=, stack(const stack&)): Make this class
uncopyable, i.e., "undefine" these operators: make them private and
don't implement them.
(clear): New.
* data/lalr1.cc: Use it instead of an assignment.
(parser): Make this class uncopyable.

data/lalr1.cc

@@ -107,6 +107,10 @@ b4_user_stype
 #endif
 
   private:
+    /// This class is not copyable.
+    ]b4_parser_class_name[ (const ]b4_parser_class_name[&);
+    ]b4_parser_class_name[& operator= (const ]b4_parser_class_name[&);
+
     /// Report a syntax error.
     /// \param loc    where the syntax error is found.
     /// \param msg    a description of the syntax error.
@@ -552,9 +556,9 @@ b4_dollar_popdef])[]dnl
        yynewstate, since the latter expects the semantical and the
        location values to have been already stored, initialize these
        stacks with a primary value.  */
-    yystate_stack_ = state_stack_type (0);
-    yysemantic_stack_ = semantic_stack_type (0);
-    yylocation_stack_ = location_stack_type (0);
+    yystate_stack_.clear ();
+    yysemantic_stack_.clear ();
+    yylocation_stack_.clear ();
     yysemantic_stack_.push (yylval);
     yylocation_stack_.push (yylloc);
 

data/stack.hh

@@ -77,6 +77,12 @@ b4_copyright([Stack handling for Bison parsers in C++],
         seq_.pop_front ();
     }
 
+    void
+    clear ()
+    {
+      seq_.clear ();
+    }
+
     inline
     unsigned int
     height () const
@@ -88,6 +94,8 @@ b4_copyright([Stack handling for Bison parsers in C++],
     inline const_iterator end () const { return seq_.rend (); }
 
   private:
+    stack (const stack&);
+    stack& operator= (const stack&);
     S seq_;
   };