Remove executable bit from file modes

[lemzwerg]

None of the files in the git repository is executable, but some of them had the executable bit set in their file mode. This was caused by two things.

• The author worked on Windows, which doesn't have the concept of an 'executable bit' for file permissions.

• The author's local clone of the git repository, while being accessed from Windows, wasn't set up correctly. This can happen, for example, if a checked-out repository gets copied from MacOS to Windows.

  A checked-out repository on Windows can be fixed by emitting the command

  git config core.fileMode false

  on the command line (or a corresponding command in a GUI).

While this is not visible on Windows, it makes a difference on both MacOS and GNU/Linux.

[mscuthbert]

Hi Werner -- this looks great. Thanks for taking the time to do it. Could you join the W3C Music Notation Community Group (signing the Community Contributor License Agreement) and then put a note here that you've joined? It's just W3C's assurance that you're freely given your contribution away. Thanks!

[lemzwerg]

Done.