Minor fixups to get 'make maintainer-check' to work.

* configure.ac: Don't use -Wnested-externs, as it's incompatible
with the new verify.h implementation.
* data/c.m4 (b4_yy_symbol_print_generate): YYUSE (yyoutput).
* data/glr.c (YYUSE): Depend on __GNUC__ as well.
* data/yacc.c (YYUSE): Likewise.
* data/lalr1.cc (yysyntax_error_): YYUSE (yystate).
* lib/subpipe.c (end_of_output_subpipe): The args are unused.
* src/parse-gram.y (declaration): Don't pass a string constant
to a function that expects char *, since GCC might complain
about the constant value.
* src/reader.c (symbol_typed_p): Add parens to pacify GCC.
* tests/cxx-type.at (_AT_TEST_GLR_CXXTYPES): #undef yylloc and yylval
before #defining them.
* tests/glr-regression.at
(Incorrectly initialized location for empty right-hand side in GLR):
In yyerror, use the msg arg.
(Corrupted semantic options if user action cuts parse):
(Incorrect lookahead during deterministic GLR):
(Incorrect lookahead during nondeterministic GLR):
Don't name a local var 'index'; it shadows string.h's 'index'.

configure.ac

@@ -1,6 +1,7 @@
 # Configure template for GNU Bison.                   -*-Autoconf-*-
 #
-# Copyright (C) 2001, 2002, 2003, 2004, 2005 Free Software Foundation, Inc.
+# Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006 Free Software
+# Foundation, Inc.
 #
 # This program is free software; you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -58,7 +59,6 @@ if test "${enableval}" = yes; then
   BISON_WARNING(-Wbad-function-cast)
   BISON_WARNING(-Wmissing-declarations)
   BISON_WARNING(-Wmissing-prototypes)
-  BISON_WARNING(-Wnested-externs)
   BISON_WARNING(-Wshadow)
   BISON_WARNING(-Wstrict-prototypes)
   AC_DEFINE([lint], 1, [Define to 1 if the compiler is checking for lint.])