Convert underscores to dashes in some %define variable names.

For now, just api.push-pull and lr.keep-unreachable-states.
Maintain old names for backward compatibility.
* NEWS (2.5): Document.
* data/c.m4 (b4_identification): Update comment.
* data/yacc.c: Update access.
* doc/bison.texinfo: Update.
* etc/bench.pl.in (bench_grammar): Update use.
* src/files.c (tr): Move to...
* src/getargs.c, src/getargs.h (tr): ... here because I can't
think of a better place to expose it.  My logic is that, for all
uses of tr so far, command-line arguments can be involved, and
getargs.h is already included.
* src/main.c (main): Update access.
* src/muscle_tab.c (muscle_percent_define_insert): Convert old
variable names to new variable names before assigning value.
* src/reader.c (reader): Update setting default.
* tests/calc.at: Update uses.
* tests/conflicts.at (Unreachable States After Conflict
Resolution): Update use.
* tests/input.at (%define enum variables): Update use.
(%define backward compatibility): New test group.
* tests/push.at: Update uses.
* tests/reduce.at: Update uses.
* tests/torture.at: Update uses.

etc/bench.pl.in

@@ -1,6 +1,6 @@
 #! /usr/bin/perl -w
 
-# Copyright (C) 2006, 2008 Free Software Foundation, Inc.
+# Copyright (C) 2006, 2008, 2009 Free Software Foundation, Inc.
 #
 # This file is part of Bison, the GNU Compiler Compiler.
 #
@@ -343,8 +343,8 @@ sub bench_grammar ($)
     (
      "pull-impure" => '',
      "pull-pure" => '%define api.pure',
-     "push-impure" => '%define api.push_pull "both"',
-     "push-pure" => '%define api.push_pull "both" %define api.pure',
+     "push-impure" => '%define api.push-pull "both"',
+     "push-pure" => '%define api.push-pull "both" %define api.pure',
     );
 
   my %bench;