Rename "default rule" to "default reduction".

This includes changing variable names in code, changing
comments, and renaming %define lr.default_rules to %define
lr.default_reductions.
* NEWS (2.5): Update IELR documentation.
* data/glr.c, data/lalr1.cc, data/lalr1.java, data/yacc.c:
Adjust YYDEFACT and yydefact_ documentation.
* doc/bison.texinfo (Decl Summary): Adjust lr.default_reductions
and lr.type documentation.  Make some other wording
improvements.
(Glossary): Adjust cross-references and Default Reduction
definition.
* src/lalr.c (state_lookahead_tokens_count): Adjust code.
Remove a confusing comment pointed out by Akim Demaille.
(initialize_LA): Adjust code.
* src/print-xml.c (print_reductions): Adjust code.
* src/print.c (print_reductions): Adjust code.
* src/reader.c (reader): Adjust code.
* src/tables.c (action_row): Adjust code.
(token_actions): Adjust code.
* src/tables.h: Adjust YYDEFACT documentation.
* tests/input.at (%define lr.default_rules invalid values):
Rename test group to...
(%define lr.default_reductions invalid values): ... this, and
update grammar file and expected output.
* tests/reduce.at (AT_TEST_LR_DEFAULT_RULES): Rename to...
(AT_TEST_LR_DEFAULT_REDUCTIONS): ... this, and update.

data/glr.c

@@ -1,8 +1,8 @@
                                                                     -*- C -*-
 
 # GLR skeleton for Bison
-# Copyright (C) 2002, 2003, 2004, 2005, 2006, 2007, 2008 Free Software
-# Foundation, Inc.
+# Copyright (C) 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009 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
@@ -150,7 +150,7 @@ m4_changecom()
 m4_divert_push(0)dnl
 @output(b4_parser_file_name@)@
 b4_copyright([Skeleton implementation for Bison GLR parsers in C],
-             [2002, 2003, 2004, 2005, 2006, 2007, 2008])
+             [2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009])
 [
 /* C GLR parser skeleton written by Paul Hilfinger.  */
 
@@ -412,9 +412,9 @@ static const ]b4_int_type_for([b4_merger])[ yymerger[] =
   ]b4_merger[
 };
 
-/* YYDEFACT[S] -- default rule to reduce with in state S when YYTABLE
-   doesn't specify something else to do.  Zero means the default is an
-   error.  */
+/* YYDEFACT[S] -- default reduction number in state S.  Performed when
+   YYTABLE doesn't specify something else to do.  Zero means the default
+   is an error.  */
 static const ]b4_int_type_for([b4_defact])[ yydefact[] =
 {
   ]b4_defact[
@@ -2639,7 +2639,7 @@ m4_if(b4_skeleton, ["glr.c"],
 [b4_defines_if(
 [@output(b4_spec_defines_file@)@
 b4_copyright([Skeleton interface for Bison GLR parsers in C],
-             [2002, 2003, 2004, 2005, 2006, 2007, 2008])
+             [2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009])
 
 b4_shared_declarations