minor clarification: rumpuser_thread_create() is used to create the host

thread context for kernel threads, never for application threads.

per discussion with justin

lib/librumpuser/rumpuser.3

@@ -1,4 +1,4 @@
-.\"     $NetBSD: rumpuser.3,v 1.16 2013/07/22 12:36:56 njoly Exp $
+.\"     $NetBSD: rumpuser.3,v 1.17 2014/02/14 00:33:51 pooka Exp $
 .\"
 .\" Copyright (c) 2013 Antti Kantee.  All rights reserved.
 .\"
@@ -23,7 +23,7 @@
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .\"
-.Dd May 15, 2013
+.Dd February 13, 2013
 .Dt RUMPUSER 3
 .Os
 .Sh NAME
@@ -455,7 +455,9 @@ The number of random bytes written into
 .Fa "int priority" "int cpuidx" "void **cookie"
 .Fc
 .Pp
-Create a thread.
+Create a schedulable host thread context.
+The rump kernel will call this interface when it creates a kernel thread.
+The scheduling policy for the new thread is defined by the hypervisor.
 In case the hypervisor wants to optimize the scheduling of the
 threads, it can perform heuristics on the
 .Fa thrname ,
@@ -465,7 +467,8 @@ and
 parameters.
 .Bl -tag -width "xenum_rumpclock"
 .It Fa fun
-function that the new thread must call
+function that the new thread must call.
+This call will never return.
 .It Fa arg
 argument to be passed to
 .Fa fun