Fix broken boost mirror for BSD and fix http -> https in some links
Summary:
Provided here: https://github.com/Bitcoin-ABC/bitcoin-abc/pull/286
I'm submitting for review since users are currently having issues receiving signup emails.
Test Plan: Read it + try to download source from the sourceforge target
Reviewers: deadalnix, Fabien, #bitcoin_abc, Mengerian
Reviewed By: #bitcoin_abc, Mengerian
Subscribers: Mengerian, teamcity, schancel
Differential Revision: https://reviews.bitcoinabc.org/D2175