Extend ACL-restriction to all Windows tools.

Protecting our processes from outside interference need not be limited
to just PuTTY: there's no reason why the other SSH-speaking tools
shouldn't have the same treatment (PSFTP, PSCP, Plink), and PuTTYgen
and Pageant which handle private key material.

unix/uxsftp.c

@@ -618,6 +618,8 @@ char *ssh_sftp_get_cmdline(const char *prompt, int no_fds_ok)
 
 void frontend_net_error_pending(void) {}
 
+void platform_psftp_post_option_setup(void) {}
+
 /*
  * Main program: do platform-specific initialisation and then call
  * psftp_main().