Fix a .Fa vs. .Fn bogon, and clarify somewhat.

lib/libc/sys/brk.2

@@ -1,4 +1,4 @@
-.\"	$NetBSD: brk.2,v 1.13 1999/03/09 20:33:22 kleink Exp $
+.\"	$NetBSD: brk.2,v 1.14 1999/03/09 20:35:18 kleink Exp $
 .\"
 .\" Copyright (c) 1980, 1991, 1993
 .\"	The Regents of the University of California.  All rights reserved.
@@ -62,7 +62,7 @@ Data addressing is restricted between
 .Fa addr
 and the lowest stack pointer to the stack segment.
 Memory is allocated by
-.Fa brk
+.Fn brk
 in page size pieces;
 if
 .Fa addr
@@ -94,11 +94,12 @@ the maximum permissible size of the
 segment;
 it will not be possible to set the break
 beyond the
+.Dv RLIMIT_DATA
 .Em rlim_max
 value returned from a call to
 .Xr getrlimit 2 ,
 e.g.
-.Dq etext + rlp\(->rlim_max.
+.Dq etext + rlim.rlim_max .
 (see
 .Xr end 3
 for the definition of
@@ -111,10 +112,10 @@ otherwise -1 with
 set to indicate why the allocation failed.
 The
 .Fn sbrk
-function returns a pointer to the base of the new storage if successful;
-otherwise -1 with
+function returns the prior break value if successful;
+otherwise ((void *)-1) is returned and
 .Va errno
-set to indicate why the allocation failed.
+is set to indicate why the allocation failed.
 .Sh ERRORS
 .Fn brk
 or