WP_HTTP: Replacing the Fsockopen & Streams Transports with a new Streams transport which fully supports HTTPS communication.
This changeset also bundles ca-bundle.crt from the Mozilla project to allow for us to verify SSL certificates on hosts which have an incomplete, outdated, or invalid local SSL configuration.
Props rmccue for major assistance getting this this far. See #25007 for discussion, also Fixes #16606 

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WP_HTTP: Re-enable curl, it was accidentally left out of [25224]. See #25007 See #16606 

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Avoid 'Only variables should be passed by reference' notice on Widgets screen. props jdgrimes. fixes #25225.
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git-svn-id: http://core.svn.wordpress.org/trunk@25196 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Upgrader: Split the UI "skins" out from the main Upgrader file into a seperate file to reduce the length of the files. See #22704

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