Fix compilation with clang

Summary: libkexiv2/src/kexiv2_p.cpp:726:9: error: token is not a valid binary operator in a preprocessor subexpression

Test Plan: Builds

Reviewers: Frameworks, cgilles, kfunk

Reviewed By: kfunk

Subscribers: kfunk

Differential Revision: https://phabricator.kde.org/D4179