Silence several warnings when building under Windows.

* agent/call-scd.c (start_scd): Replace int by assuan_fd_t.
(start_pinentry): Ditto.
* common/asshelp.c (start_new_gpg_agent): Replace int by assuan_fd_t.
* common/dotlock.c (GNUPG_MAJOR_VERSION): Include stringhelp.h for
prototypes on Windows and some other platforms.
* common/logging.c (fun_writer): Declare addrbuf only if needed.
* g10/decrypt.c (decrypt_message_fd) [W32]: Return not_implemented.
* g10/encrypt.c (encrypt_crypt) [W32]: Return error if used in server
mode.
* g10/dearmor.c (dearmor_file, enarmor_file): Replace GNUPG_INVALID_FD
by -1 as temporary hack for Windows.
* g10/export.c (do_export): Ditto.
* g10/revoke.c (gen_desig_revoke, gen_revoke): Ditto.
* g10/sign.c (sign_file, clearsign_file, sign_symencrypt_file): Ditto.
* g10/server.c (cmd_verify, gpg_server) [W32]: Return an error.
--

The gpg server mode is not actual working and thus we can avoid the
warnings by explicitly disabling the mode.  We keep it working under
Unix, though.

agent/call-scd.c

@@ -198,7 +198,7 @@ start_scd (ctrl_t ctrl)
   const char *pgmname;
   assuan_context_t ctx = NULL;
   const char *argv[3];
-  int no_close_list[3];
+  assuan_fd_t no_close_list[3];
   int i;
   int rc;
 
@@ -324,7 +324,7 @@ start_scd (ctrl_t ctrl)
         no_close_list[i++] = assuan_fd_from_posix_fd (log_get_fd ());
       no_close_list[i++] = assuan_fd_from_posix_fd (fileno (stderr));
     }
-  no_close_list[i] = -1;
+  no_close_list[i] = ASSUAN_INVALID_FD;
 
   /* Connect to the pinentry and perform initial handshaking.  Use
      detached flag (128) so that under W32 SCDAEMON does not show up a