We should standardise on curl for external access because it supports a lot of things like SSL which we need more and more. Moodle Networking requires it.

We can do this in a compatible way by including the libcurlemu project in Moodle:

http://code.blitzaffe.com/pages/phpclasses/category/52/fileid/7

Once this is added, code in a few places should be converted to use it. (downloading lang packs, timezones, etc).