Remove curl context (php#2270)

This was removed in PHP 5.5: https://wiki.php.net/rfc/curl-wrappers-removal-rfc

Author: KapitanOczywisty

language/context.xml

@@ -18,7 +18,6 @@
  &language.context.http;
  &language.context.ftp;
  &language.context.ssl;
- &language.context.curl;
  &language.context.phar;
  &language.context.parameters;
  &language.context.zip;