* include/sys/cygwin.h: Add new cygwin_getinfo_type

CW_SET_EXTERNAL_TOKEN.
	Add new enum CW_TOKEN_IMPERSONATION, CW_TOKEN_RESTRICTED.
	* cygheap.h (cyguser): New flags ext_token_is_restricted,
	curr_token_is_restricted and setuid_to_restricted.
	* external.cc (cygwin_internal): Add CW_SET_EXTERNAL_TOKEN.
	* sec_auth.cc (set_imp_token): New function.
	(cygwin_set_impersonation_token): Call set_imp_token ().
	* security.h (set_imp_token): New prototype.
	* spawn.cc (spawn_guts): Use CreateProcessAsUserW if restricted token
	was enabled by setuid().  Do not create new window station in this case.
	* syscalls.cc (seteuid32): Add handling of restricted external tokens.
	Set HANDLE_FLAG_INHERIT for primary token.
	(setuid32): Set setuid_to_restricted flag.
	* uinfo.cc (uinfo_init): Do not reimpersonate if restricted token was
	enabled by setuid ().  Initialize user.*_restricted flags.

winsup/cygwin/external.cc

@@ -415,6 +415,13 @@ cygwin_internal (cygwin_getinfo_types t, ...)
 	  int useTerminateProcess = va_arg (arg, int);
 	  exit_process (status, !!useTerminateProcess); /* no return */
 	}
+      case CW_SET_EXTERNAL_TOKEN:
+	{
+	  HANDLE token = va_arg (arg, HANDLE);
+	  int type = va_arg (arg, int);
+	  set_imp_token (token, type);
+	  return 0;
+	}
 
       default:
 	break;