FreeBSD does not need extern char *sys_errlist[]

Add preprocessor directives not to try
to redefine sys_errlist[] or sys_nerr

There are already definitions:

 extern __const char *__const sys_errlist[];
 extern __const int sys_nerr;

in <stdio.h>

Actually we should have something like
NeedSysErrlist in imake definitions
to get rid of those #ifdefs.

cde/programs/dtimsstart/remote.c

@@ -37,7 +37,7 @@
 #include	<X11/Xproto.h>		/* for X_ChangeHosts */
 #include	<X11/Xatom.h>		/* for XA_STRING */
 
-#if !defined(linux)
+#if !defined(linux) && !defined(__FreeBSD__)
 extern char	*sys_errlist[];
 #endif
 

cde/programs/dtimsstart/start.c

@@ -32,7 +32,7 @@
 #define _NFILE FOPEN_MAX
 #endif
 
-#if !defined(linux)
+#if !defined(linux) && !defined(__FreeBSD__)
 extern char	*sys_errlist[];
 extern int	sys_nerr;
 #endif