add startupasfs from sources

Reference: /n/atom/patch/applied/startupasfs
Date: Wed Feb 26 20:13:30 CET 2014
Signed-off-by: quanstro@quanstro.net

--- /rc/bin/startupasfs	Thu Jan  1 00:00:00 1970
+++ /rc/bin/startupasfs	Wed Feb 26 20:13:08 2014
@@ -0,0 +1,5 @@
+#!/bin/rc
+# startupasfs - start upas/fs if needed, mainly for lib/profile
+if (! test -e /srv/upasfs.$user)
+	upas/fs -s
+mount -c /srv/upasfs.$user /mail/fs