Fix typo which caused Plan 9 image files to be treated as suspect mail attachments.

Reference: /n/sources/patch/applied/vf-p9image
Date: Fri Jan 15 18:19:18 CET 2010
Signed-off-by: miller@hamnavoe.com

--- /mail/lib/validateattachment	Fri Jan 15 18:18:23 2010
+++ /mail/lib/validateattachment	Fri Jan 15 18:18:20 2010
@@ -46,7 +46,7 @@
 		exit discard
 	}
 
-case jpeg 'PNG image' bmp 'GIF image' *'plan 9 image'
+case jpeg 'PNG image' bmp 'GIF image' *'plan 9 image'*
 	save accept
 	exit accept