Do not classname-qualify members of enums.

[bangerth]

This is only allowed in C++11, whereas in C++98 the names of members of an enum
are only part of the enclosing namespace, but not members of the enum's namespace
itself.

[bangerth]

I should say that I needed to qualify the names by the namespace-name because there is also a function initialize in the class where I use these names. Consequently, leaving them unqualified left things ambiguous for the initialize case. I chose to also namespace-qualify the other uses of the enum members then.

[gassmoeller]

Thanks for fixing!