add pragma for threadsetname

Reference: /n/atom/patch/applied/threadsetnamearg
Date: Sat May  3 16:27:56 CES 2014
Signed-off-by: quanstro@quanstro.net

--- /sys/include/thread.h	Sat May  3 16:27:53 2014
+++ /sys/include/thread.h	Sat May  3 16:27:53 2014
@@ -109,6 +109,8 @@
 void	**tprivaddr(int);
 void	yield(void);
 
+#pragma	varargck	argpos	threadsetname	1
+
 extern	int	mainstacksize;
 
 /* slave I/O processes */