tcpd.h: add prototype for hosts_ctl

According the hosts_access(3) man page the hosts_ctl() prototype
should be in tcpd.h. For now, follow other declarations and don't
add the arguments in the prototype.

Reference:
https://www.illumos.org/issues/4385

PR:		32808
MFC after:	2 weeks

contrib/tcp_wrappers/tcpd.h

@@ -73,6 +73,7 @@ extern void fromhost();			/* get/validate client host info */
 #endif
 
 extern int hosts_access();		/* access control */
+extern int hosts_ctl();			/* wrapper around request_init() */
 extern void shell_cmd();		/* execute shell command */
 extern char *percent_x();		/* do %<char> expansion */
 extern void rfc931();			/* client name from RFC 931 daemon */