resolv: Add a required include to resolv.h

Add a required include to resolv.h for sockaddr_in.  This should reduce
patching required when porting code written with Linux or NetBSD in mind.

PR:		182466
MFC after:	1 week

(cherry picked from commit 58cf91d3b7)

include/resolv.h

@@ -59,6 +59,7 @@
 #include <sys/cdefs.h>
 #include <sys/socket.h>
 #include <stdio.h>
+#include <netinet/in.h>
 #include <arpa/nameser.h>
 
 /*%

lib/libc/net/resolver.3

@@ -27,7 +27,7 @@
 .\"
 .\"     @(#)resolver.3	8.1 (Berkeley) 6/4/93
 .\"
-.Dd September 15, 2022
+.Dd January 8, 2024
 .Dt RESOLVER 3
 .Os
 .Sh NAME
@@ -47,9 +47,6 @@
 .Sh LIBRARY
 .Lb libc
 .Sh SYNOPSIS
-.In sys/types.h
-.In netinet/in.h
-.In arpa/nameser.h
 .In resolv.h
 .Ft int
 .Fo res_query