Use full "(?P<name>" syntax for named captures in HTTPFuture

Summary:
Some versions of PCRE reject the short "(?<" form and require "(?P<".

Also support use of non-default ports for Conduit.

Test Plan:
Will make cllorca apply this patch and tell me it fixes his problem.

Reviewers: llorca, toulouse
Commenters: llorca
CC: aran, epriestley, llorca
Differential Revision: 495