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'.

lib/subpipe.c

@@ -1,6 +1,6 @@
 /* Subprocesses with pipes.
 
-   Copyright (C) 2002, 2004, 2005 Free Software Foundation, Inc.
+   Copyright (C) 2002, 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
@@ -71,6 +71,18 @@
 #include "gettext.h"
 #define _(Msgid)  gettext (Msgid)
 
+#ifndef __attribute__
+/* This feature is available in gcc versions 2.5 and later.  */
+# if !defined (__GNUC__) || __GNUC__ < 2 || \
+(__GNUC__ == 2 && __GNUC_MINOR__ < 5) || __STRICT_ANSI__
+#  define __attribute__(Spec) /* empty */
+# endif
+#endif
+
+#ifndef ATTRIBUTE_UNUSED
+# define ATTRIBUTE_UNUSED __attribute__ ((__unused__))
+#endif
+
 
 /* Initialize this module.  */
 
@@ -168,6 +180,7 @@ reap_subpipe (pid_t pid, char const *program)
 }
 
 void
-end_of_output_subpipe (pid_t pid, int fd[2])
+end_of_output_subpipe (pid_t pid ATTRIBUTE_UNUSED,
+		       int fd[2] ATTRIBUTE_UNUSED)
 {
 }