Define NI_MAXSERV if not defined by operating system

I found I needed NI_MAXSERV as it is defined in netdb.h, which is
not included by daemon.c.  Rather than including the whole header
we can define a reasonable fallback value.
Signed-off-by: NShawn O. Pearce <spearce@spearce.org>

daemon.c

@@ -9,6 +9,10 @@
 #define HOST_NAME_MAX 256
 #endif
 
+#ifndef NI_MAXSERV
+#define NI_MAXSERV 32
+#endif
+
 static int log_syslog;
 static int verbose;
 static int reuseaddr;