Handle deficiencies in PHP's parse_url in older versions of PHP (<5.4.7) in WP_HTTP::make_absolute_url().

In older versions of PHP:
- parse_url() will fail to parse a url where the scheme break (://) is present in a relative URL's path
- parse_url() will include the hostname of a schemeless URL in the path component

This handles those two types of URL's by correcting the response from parse_url().

Fixes #28001, #29886

Built from https://develop.svn.wordpress.org/trunk@29861


git-svn-id: http://core.svn.wordpress.org/trunk@29621 1a063a9b-81f0-0310-95a4-ce76da25c4cd