perlbug: Allow noninteractive use in test mode (-t option)

This is groundworks for perlbug unit tests.

Not all of the interactive questions can be overridden on
the command line, so we will have to pipe in commands.

Adapt the test mode ("-t"), which used to just override the
recipient address, for this rather than inventing one more
new option.

utils/perlbug.PL

@@ -101,7 +101,7 @@ Init();
 
 if ($opt{h}) { Help(); exit; }
 if ($opt{d}) { Dump(*STDOUT); exit; }
-if (!-t STDIN && !($ok and not $opt{n})) {
+if (!-t STDIN && !$opt{t} && !($ok and not $opt{n})) {
     paraprint <<"EOF";
 Please use $progname interactively. If you want to
 include a file, you can use the -f switch.
@@ -1526,6 +1526,8 @@ supply one on the command line.
 =item B<-t>
 
 Test mode.  The target address defaults to B<perlbug-test@perl.org>.
+Also makes it possible to command perlbug from a pipe or file, for
+testing purposes.
 
 =item B<-T>