Patch: fix priority flags management in TnyCamelMsgHeader

[Jose Dapena Paz <jdapena igalia com>]

	Hi,

	This patch fixes some pending issues with priority handling in
tinymail, after last changes.

	With the previous code:
	* If you set a non priority flag, priority flag was always set to
NORMAL.
	* If you unset a non priority flag, priority flag was alwasa set to
NORMAL

	With the new code these issues should be fixed:
	* We only change the priority flag if we set low or high  priorities,
or if we set 0 flags (normal priority).
	* We set the priority to normal if we unset any priority flag.

-- 
Jose Dapena Paz <jdapena igalia com>
Igalia

Index: libtinymail-camel/tny-camel-msg-header.c
===================================================================
--- libtinymail-camel/tny-camel-msg-header.c	(revision 2887)
+++ libtinymail-camel/tny-camel-msg-header.c	(working copy)
@@ -255,10 +255,12 @@
 			me->partial = FALSE;
 	}
 
-	camel_medium_remove_header (CAMEL_MEDIUM (me->msg), "X-MSMail-Priority");
-	camel_medium_remove_header (CAMEL_MEDIUM (me->msg), "X-Priority");
+	if ((mask & TNY_HEADER_FLAG_PRIORITY_MASK)|| (mask == 0)) {
+		camel_medium_remove_header (CAMEL_MEDIUM (me->msg), "X-MSMail-Priority");
+		camel_medium_remove_header (CAMEL_MEDIUM (me->msg), "X-Priority");
 
-	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");
@@ -277,7 +279,10 @@
 		tny_header_set_flags (me->decorated, mask);
 	}
 
-	set_prio_mask (me, mask);
+	/* we only need to detect unsets of low and high priority, as unsetting normal
+	 * priority should lead to set again normal priority */
+	if (mask & TNY_HEADER_FLAG_PRIORITY_MASK)
+		set_prio_mask (me, TNY_HEADER_FLAG_NORMAL_PRIORITY);
 
 	if (mask & TNY_HEADER_FLAG_ATTACHMENTS)
 		camel_medium_remove_header (CAMEL_MEDIUM (me->msg), "X-MS-Has-Attach");