java: use SymbolType

The Java enums are very different from the C model.  As a consequence,
one cannot "build" an enum directly from an integer, we must retrieve
it.  That's the purpose of the SymbolType.get class method.

* data/skeletons/java.m4 (b4_symbol_enum, b4_case_code_symbol)
(b4_declare_symbol_enum): New.
* data/skeletons/lalr1.java: Use SymbolType,
SymbolType.YYSYMBOL_YYEMPTY, etc.
* examples/java/calc/Calc.y, tests/local.at: Adjust.

examples/java/calc/Calc.y

@@ -121,15 +121,15 @@ class CalcLexer implements Calc.Lexer {
     System.err.print (ctx.getLocation () + ": syntax error");
     {
       final int TOKENMAX = 10;
-      int[] arg = new int[TOKENMAX];
+      Calc.SymbolType[] arg = new Calc.SymbolType[TOKENMAX];
       int n = ctx.yyexpectedTokens (arg, TOKENMAX);
       for (int i = 0; i < n; ++i)
         System.err.print ((i == 0 ? ": expected " : " or ")
                           + ctx.yysymbolName (arg[i]));
     }
     {
-      int lookahead = ctx.getToken ();
-      if (lookahead != ctx.EMPTY)
+      Calc.SymbolType lookahead = ctx.getToken ();
+      if (lookahead != Calc.SymbolType.YYSYMBOL_YYEMPTY)
         System.err.print (" before " + ctx.yysymbolName (lookahead));
     }
     System.err.println ("");