gettimeofday cannot be used to reliably implement high precision process synchronization

The use of gettimeofday in time_sleep_until is technically incorrect, it's not possible
to use gettimeofday in this way reliably on any platform: It relies on operating system
global structures, which may be modified by any other process on the system at any time.

While in practice, users may be ignoring this flaw, it entirely depends on the other software
running on the system to which the application is deployed, there is no possible way to write
a test that will always pass on any system, therefore it must be marked XFAIL.

Author: krakjoe

ext/standard/tests/misc/time_sleep_until_basic.phpt

@@ -32,3 +32,5 @@ Michele Orselli [email protected]
 --EXPECT--
 bool(true)
 bool(true)
+--XFAIL--
+gettimeofday cannot be used to reliably implement high precision process synchronization