Expand tabs in diagnostics.pm

Otherwise pod like this:

The second situation is caused by an eval accessing a lexical subroutine
that has gone out of scope, for example,

    sub f {
	my sub a {...}
	sub { eval '\&a' }
    }
    f()->();

is turned into this:

    The second situation is caused by an eval accessing a variable that has
    gone out of scope, for example,

        sub f {
    	my $a;
    	sub { eval '$a' }
        }
        f()->();

instead of this:

    The second situation is caused by an eval accessing a variable that has
    gone out of scope, for example,

        sub f {
            my $a;
            sub { eval '$a' }
        }
        f()->();

I don’t know how to test this without literally copying and pasting
parts of diagnostics.pm into diagnostics.t.  But I have tested it man-
ually and it works.

1 files changed, 2 insertions, 0 deletions

diff --git a/lib/diagnostics.pm b/lib/diagnostics.pm
index a85f282044..40c6748c57 100644
--- a/lib/diagnostics.pm
+++ b/lib/diagnostics.pm
@@ -194,6 +194,7 @@ our $TRACEONLY = 0;
 our $WARNTRACE = 0;
 
 use Config;
+use Text::Tabs 'expand';
 my $privlib = $Config{privlibexp};
 if ($^O eq 'VMS') {
     require VMS::Filespec;
@@ -366,6 +367,7 @@ my %msg;
 		{
 		    next;
 		}
+		$_ = expand $_;
 		s/^/    /gm;
 		$msg{$header} .= $_;
 		for my $h(@headers) { $msg{$h} .= $_ }