* NEWS: Version 2.1.

* NEWS: Remove notice of yytname change, since it was never in an
official release.
* data/glr.c (yydestroyGLRState): Rename local var to avoid shadowing
diagnostic.
* src/output.c (prepare): Likewise.
* data/lalr1.cc (YYERROR_VERBOSE_IF): New macro.
(yysyntax_error_): Use it to avoid GCC warning when YYERROR_VERBOSE
is not defined.  This is an awful hack, but it's enough for now.
All callers changed.
* tests/glr-regression-at (make_value): Args are const pointers now,
to avoid GCC warning.
(Duplicated user destructor for lookahead): New test.  Currently
skipped.  It fails on my host but I'm not sure it'll always fail.