Fix bad .Xr and some .Nm abuse

lib/libc/sys/brk.2

@@ -1,4 +1,4 @@
-.\"	$NetBSD: brk.2,v 1.11 1998/04/28 22:28:30 fair Exp $
+.\"	$NetBSD: brk.2,v 1.12 1998/04/29 19:19:15 fair Exp $
 .\"
 .\" Copyright (c) 1980, 1991, 1993
 .\"	The Regents of the University of California.  All rights reserved.
@@ -83,7 +83,7 @@ to the next page boundary.
 .\" .Nm sbrk .
 .\" .Pp
 The current value of the program break is reliably returned by
-.Dq Li sbrk(0)
+.Fn sbrk 0
 (see also
 .Xr end 3 ) .
 The
@@ -104,21 +104,21 @@ e.g.
 for the definition of
 .Em etext ) .
 .Sh RETURN VALUES
-.Nm brk
+.Fn brk
 returns 0 if successful;
 otherwise -1 with
 .Va errno
 set to indicate why the allocation failed.
 The
-.Nm sbrk
+.Fn sbrk
 function returns a pointer to the base of the new storage if successful;
 otherwise -1 with
 .Va errno
 set to indicate why the allocation failed.
 .Sh ERRORS
-.Xr brk
+.Fn brk
 or
-.Xr sbrk
+.Fn sbrk
 will fail and no additional memory will be allocated if
 one of the following are true:
 .Bl -tag -width Er