Remove use of static::

Breaks 5.2. This fixes googleapis#124

Author: Ian Barber

src/Google/IO/Curl.php

@@ -130,6 +130,6 @@ protected function _needsQuirk()
  {
  $ver = curl_version();
  $versionNum = $ver['version_number'];
- return $versionNum < static::NO_QUIRK_VERSION;
+ return $versionNum < Google_IO_Curl::NO_QUIRK_VERSION;
  }
 }