add include of prmon.h to fix build bustage

mailnews/imap/src/nsImapMailFolder.h

@@ -39,7 +39,7 @@
 #include "nsIMsgMessageService.h"
 #include "nsIMsgFilterHitNotify.h"
 #include "nsIMsgFilterList.h"
-
+#include "prmon.h"
 class nsImapMoveCoalescer;