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.

TODO

@@ -5,6 +5,9 @@
 - YYNOMEM
 - i18n in Java
 
+** Java
+Check api.token.raw
+
 ** Naming conventions
 yysyntax_error_arguments should be yy_syntax_error_arguments, since it's a
 private implementation detail.