skeletons: use "end of file" instead of "$end"

The name "$end" is nice in the report, in particular it avoids that
pointed-rules (aka items) be too long.  It also helps keeping them
"standard".

But it is bad in error messages, we should report "end of file" (or
maybe "end of input", this is debatable).  So, unless the user already
defined the alias for the error token herself, make it "end of file".
It should even be translated if the user already translated some
tokens, so that there is now no strong reason to redefine the $end
token.

* src/output.c (prepare_symbol_names): Issue "end of file" instead of
"$end".

* data/skeletons/lalr1.java (yytnamerr_): Remove the renaming hack.

* build-aux/update-test: Accept files with names containing a "+",
such as c++.at.
* tests/actions.at, tests/c++.at, tests/conflicts.at,
* tests/glr-regression.at, tests/regression.at, tests/skeletons.at:
Adjust.

data/skeletons/lalr1.java

@@ -1080,9 +1080,6 @@ b4_dollar_popdef[]dnl
               return yyr.toString ();
             }
       }
-    else if (yystr.equals ("$end"))
-      return "end of input";
-
     return yystr;
   }