Update qimport help explaining how to read a patch from stdin (Issue371)

Update qimport help explaining how to read a patch from stdin (Issue371)

--- a/hgext/mq.py	Thu Apr 16 15:34:03 2009 +0200
+++ b/hgext/mq.py	Sat Apr 18 00:21:11 2009 -0700
@@ -1683,6 +1683,10 @@
     format. See the diffs help topic for information on why this is
     important for preserving rename/copy information and permission
     changes.
+
+    To import a patch from standard input, pass - as the patch file.
+    When importing from standard input, a patch name must be specified
+    using the --name flag.
     """
     q = repo.mq
     q.qimport(repo, filename, patchname=opts['name'],