fix for high-prio messages that have attachments

["Dirk-Jan C. Binnema" <dirk-jan binnema nokia com>]

High-priority messages which also have an attachment,
seem to forget that they are high-priority messages.

Attached patch seems to fix this. It seems the logic got
reverted. Admittedly, I don't fully understand the
binary acrobatics involved. 

Best wishes,
Dirk.

Index: tny-camel-msg-header.c
===================================================================
--- tny-camel-msg-header.c	(revision 2979)
+++ tny-camel-msg-header.c	(working copy)
@@ -258,11 +258,7 @@
 			me->partial = FALSE;
 	}
 
-	/* Set priority only if no other flags are found.
-	   Normal priority is 00 so there's no other way to detect it */
-	if (!(mask & ~TNY_HEADER_FLAG_PRIORITY_MASK)) {
-		set_prio_mask (me, mask);
-	}
+	set_prio_mask (me, mask);
 
 	if (mask & TNY_HEADER_FLAG_ATTACHMENTS) {
 		camel_medium_remove_header (CAMEL_MEDIUM (me->msg), "X-MS-Has-Attach");