As instrumentsxml.h is never touched by a C/C++ compiler, 8-bit ASCII and UTF-8 characters should never cause any kind of comapitibilty or standards compliance problems, and actually never had so far with at
least the ♭ being used in multiple places, so we can as well have ü, č and Č there too.
So fix Güiro in other places too, in C++ code in a C++11 compatible manner.
While at it fix some duplicate short instrument names and also a fix/workaround for an lupdate diagnostic
adding semicolons for Q_DECLARE_METATYPE() and
Q_DECLARE_OPERATORS_FOR_FLAGS(), removing semicolons from Q_PROPERTY()
(QtCreator complains about them) and fixing a comment, reformatting for
alignment
