remove the remark that lksh is not suitable for /bin/sh

(as, on some systems and for some pedants, it may be *better* suited
 due to its broken use of the host C “long” data type for arithmetics)
but warn that this can only work with -DMKSH_BINSHPOSIX really

lksh.1

@@ -1,4 +1,4 @@
-.\" $MirOS: src/bin/mksh/lksh.1,v 1.4 2013/05/02 20:21:43 tg Exp $
+.\" $MirOS: src/bin/mksh/lksh.1,v 1.5 2013/05/22 18:18:06 tg Exp $
 .\"-
 .\" Copyright (c) 2008, 2009, 2010, 2012, 2013
 .\"	Thorsten “mirabilos” Glaser <tg@mirbsd.org>
@@ -72,7 +72,7 @@
 .\" with -mandoc, it might implement .Mx itself, but we want to
 .\" use our own definition. And .Dd must come *first*, always.
 .\"
-.Dd $Mdocdate: May 2 2013 $
+.Dd $Mdocdate: May 22 2013 $
 .\"
 .\" Check which macro package we use, and do other -mdoc setup.
 .\"
@@ -179,10 +179,6 @@ has the following differences from
 .Nm mksh :
 .Bl -bullet
 .It
-.Nm
-is not suitable for use as
-.Pa /bin/sh .
-.It
 There is no explicit support for interactive use,
 nor any command line editing or history code.
 Hence,
@@ -262,6 +258,14 @@ does not keep file descriptors \*(Gt 2 private.
 .Pp
 .Pa https://www.mirbsd.org/ksh\-chan.htm
 .Sh CAVEATS
+To use
+.Nm
+as
+.Pa /bin/sh ,
+compilation to enable
+.Ic set -o posix
+by default is highly recommended for better standards compliance.
+.Pp
 .Nm
 tries to make a cross between a legacy bourne/posix compatibl-ish
 shell and a legacy pdksh-alike but