Use WP's _http_build_query instead of PHP's http_build_query.

Wait for a major version bump before introducing something that breaks based on the PHP version being used, since we are technically still PHP 4.*-compatible.


git-svn-id: https://plugins.svn.wordpress.org/akismet/trunk@967479 b8457f37-d9ea-0310-8a92-e5e31aec5664