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

include/resolv.h

@@ -58,6 +58,7 @@
 #include <sys/cdefs.h>
 #include <sys/socket.h>
 #include <stdio.h>
+#include <netinet/in.h>
 #include <arpa/nameser.h>
 
 /*%

lib/libc/net/resolver.3

@@ -25,7 +25,7 @@
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .\"
-.Dd September 15, 2022
+.Dd January 8, 2024
 .Dt RESOLVER 3
 .Os
 .Sh NAME
@@ -45,9 +45,6 @@
 .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