fix_messageparser_interaction

Fix hang during t/3_while test with recent Mail::Mbox::MessageParser.
See Debian bug #395268.
Patch by David Coppit <david@coppit.org>

--- MboxParser.pm
+++ MboxParser.pm
@@ -519,7 +519,6 @@
 
     return undef if ref(\$p) eq 'SCALAR' or $p->end_of_file;
 
-    seek $self->{READER}, $self->{CURR_POS}, SEEK_SET;
     my $nl = $self->{NL};
     my $mailref = $p->read_next_email;
     my ($header, $body) = split /$nl$nl/, $$mailref, 2;
@@ -793,7 +792,8 @@
     my $self = shift;
     my $h = $self->{READER};
     my $newline;
-    
+
+    my $old_position = tell $h;
     seek $h, 0, SEEK_SET;
     while (sysread $h, (my $c), 1) {
         if (ord($c) == 13) {
@@ -807,6 +807,7 @@
             last;
         }
     }
+    seek($h, $old_position, 0);
     return $newline;
 }