Fix compile warnings with clang

Summary:
I'm fairly sure '!=' is the intended meaning in the first two hunks.

No idea at all what the bit-hack-with-narrowing-conversions is meant to do, but nothing actually seems to use it (in any kdev*).

Test Plan: Compiles, the tests pass. kdev-php hasn't obviously blown up.

Reviewers: KDevelop, kfunk

Reviewed By: KDevelop, kfunk

Subscribers: kfunk, apol, kdevelop-devel

Differential Revision: https://phabricator.kde.org/D5125