Fix typo

src/lib/libc/stdlib/system.3

@@ -33,7 +33,7 @@
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .\"
-.\"     $OpenBSD: system.3,v 1.4 1996/08/19 08:33:53 tholo Exp $
+.\"     $OpenBSD: system.3,v 1.5 1996/12/11 23:09:53 tholo Exp $
 .\"
 .Dd June 29, 1991
 .Dt SYSTEM 3
@@ -95,4 +95,4 @@ function
 conforms to
 .St -ansiC 
 and
-.St -1003.2-92 .
+.St -p1003.2-92 .