Revert union gdb_sockaddr_u

Revert union gdb_sockaddr_u

This reverts 366c75fc.

We don't actually need to access the object through
"struct sockaddr *", so we don't need the union:
   https://sourceware.org/ml/gdb-patches/2015-03/msg00213.html

gdb/ChangeLog:
2015-03-09  Pedro Alves  <palves@redhat.com>

	Revert:
	2015-03-07  Pedro Alves  <palves@redhat.com>
	* common/gdb_socket.h: New file.
	* ser-tcp.c: Include gdb_socket.h.  Don't include netinet/in.h nor
	sys/socket.h.
	(net_open): Use union gdb_sockaddr_u.

gdb/gdbserver/ChangeLog:
2015-03-09  Pedro Alves  <palves@redhat.com>

	Revert:
	2015-03-07  Pedro Alves  <palves@redhat.com>
	* gdbreplay.c: No longer include <netinet/in.h>, <sys/socket.h>,
	or <winsock2.h> here.  Instead include "gdb_socket.h".
	(remote_open): Use union gdb_sockaddr_u.
	* remote-utils.c: No longer include <netinet/in.h>, <sys/socket.h>
	or <winsock2.h> here.  Instead include "gdb_socket.h".
	(handle_accept_event, remote_prepare): Use union gdb_sockaddr_u.
	* tracepoint.c: Include "gdb_socket.h" instead of <sys/socket.h>
	or <sys/un.h>.
	(init_named_socket, gdb_agent_helper_thread): Use union
	gdb_sockaddr_u.