libcody: Include <netinet/in.h> as needed

libcody: Include <netinet/in.h> as needed

libcody as originally added to GCC fail to build on *-unknown-freebsd11.4
and presumably others:

  c++ -std=c++11 -g -include config.h -I ... -MMD -MP -MF netclient.d -c
    -o netclient.o
  .../libcody/netclient.cc:114:3: error: unknown type sockaddr_in6 addr;
                                                      ^~~~~~~~~~~~

sockaddr_in6 is declared in /usr/include/netinet6/in6.h,
which is included by /usr/include/netinet/in.h.

Indeed, per https://man7.org/linux/man-pages/man7/ipv6.7.html

    #include <sys/socket.h>
    #include <netinet/in.h>

should be included, and our own gcc/ada/gsocket.h also has

    #if !(defined (VMS) || defined (__MINGW32__))
    #include <sys/socket.h>
    #include <sys/un.h>
    #include <netinet/in.h>
    :
    #endif

libcody/ChangeLog:

2020-12-21  Gerald Pfeifer  <gerald@pfeifer.com>

	* netserver.cc: Include <netinet/in.h>.