fixupdiff: actually apply the DIFadd/DIFdel hack

looks like recent changes made it inactive: must
change $line, not $_.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

git-svn-id: https://tools.oasis-open.org/version-control/svn/virtio/branches/v1.0@562 0c8fb4dd-22a2-4bb5-bc14-6c75a5f43652

fixupdiff.pl

@@ -26,8 +26,8 @@
 	# As a result, number of \color directives goes does sufficiently
 	# enough to avoid the overflow error.
 
-	s/\\DIFdelbegin \\DIFdel\{([^}]*)\}\\DIFdelend/\\DIFdeltext{$1}/;
-	s/\\DIFaddbegin \\DIFadd\{([^}]*)\}\\DIFaddend/\\DIFaddtext{$1}/;
+	$line =~ s/\\DIFdelbegin \\DIFdel\{([^}]*)\}\\DIFdelend/\\DIFdeltext{$1}/;
+	$line =~ s/\\DIFaddbegin \\DIFadd\{([^}]*)\}\\DIFaddend/\\DIFaddtext{$1}/;
 
 	print $line;
 	if (m/%DIFDELCMD\s+<\s+\\end\{lstlisting\}/) {