openocd: fix issue in WIN32 with TCP adapters

Issue: server_quit is called before adapter_quit:
  In WIN32 only in server_quit we do an WSACleanup,
  which terminates/closes all active sockets.
  So if the adapter is TCP based, the adapter.quit handler
  will fail if it will need to send some commands through TCP.

Example: close_socket in jtag_vpi_quit will fail in WIN32
  because the socket is already closed
  and the errno is set as "Bad File Descriptor"

To fix that we introduced new functions called server_host_os_entry/quit
to manage specific OS setup (hence WSA for sockets in WINDOWS) in order
to delay WSACleanup after adapter_quit().

Change-Id: Ie4afacafe123857f6ae300e376bdfcf0d8c027ac
Signed-off-by: Tarek BOCHKATI <tarek.bouchkati@gmail.com>
Reviewed-on: http://openocd.zylin.com/5456
Tested-by: jenkins
Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com>

src/server/server.h

@@ -80,6 +80,9 @@ int add_service(char *name, const char *port,
 		void *priv);
 int remove_service(const char *name, const char *port);
 
+int server_host_os_entry(void);
+int server_host_os_close(void);
+
 int server_preinit(void);
 int server_init(struct command_context *cmd_ctx);
 int server_quit(void);