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.

TODO

@@ -6,6 +6,7 @@
 - i18n in Java
 - symbol.type_get should be kind_get, and it's not documented.
 - token code instead of token user number etc.
+- YYERRCODE and "end of file" and translation
 
 ** User token number, internal symbol number, external token number, etc.
 There is some confusion over these terms, which is even a problem for
@@ -43,10 +44,6 @@ I feel it's ugly to use the GNU style to declare functions in the doc.  It
 generates tons of white space in the page, and may contribute to bad page
 breaks.
 
-** improve syntax errors (UTF-8, internationalization)
-While at it, we should stop using "$end" by default, in favor of "end of
-file", or "end of input", whatever.  See how lalr1.java does that.
-
 ** consistency
 token vs terminal, variable vs non terminal.