macros: give names to anonymous enums

GCC 4.2 (at least on MacOS) does not compile with anonymous enums for
exponentToMultiplier. Therefore just use some internal name to get it to
compile.

closes #641

Many thanks to Chiara Zampolli for testing the necessary changes!

Signed-off-by: Matthias Kretz <kretz@kde.org>
Merge remote-tracking branch 'origin/0.7' into 0.7