Fix profiling Conduit calls

Summary: This error was masked by resolving HTTPS futures in serial.

Test Plan:
  PhutilServiceProfiler::getInstance()->enableDiscardMode();
  $conduit = new ConduitClient('https://secure.phabricator.com/');
  $futures = array(
    $conduit->callMethod('conduit.ping', array()),
    $conduit->callMethod('conduit.ping', array()),
  );

  Futures($futures)->resolveAll();

Didn't see:

> Notice: Undefined offset: 2 in libphutil/src/serviceprofiler/PhutilServiceProfiler.php on line 42

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, Korvin

Differential Revision: https://secure.phabricator.com/D5027
Fix generating random bytes under Windows

Summary: I'm hopefully the only user of this.

Test Plan:
  $ arc unit

See no more:

> Uninitialized string offset: 19 at [libphutil/src/filesystem/Filesystem.php:394]

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, Korvin

Differential Revision: https://secure.phabricator.com/D5029