Enable C++ 11 support

Please report a bug at https://bugs.kde.org/ if this breaks your
build system / compiler for some reason.

The plan for now is to use only those C++ 11 features that are
supported by MSVC 10.0 and later.

See also
https://www.mail-archive.com/marble-devel@kde.org/msg01736.html

(cherry picked from commit 250137c8)