Import upstream commit to get rid of old cmake syntax

Summary:
This imports 8bc55218 "cmake: get rid of the old & ugly syntax of having
arguments in else(), endif(), endmacro(), endfunction()" from
https://github.com/TelepathyIM/telepathy-qt.

Reviewers: KDE Telepathy, akulichalexandr, davidedmundson

Differential Revision: https://phabricator.kde.org/D7507