Change Aeolus default to Equal Temperament

The default Aeolus temperament was Mean Tone which sounds out of tune to
our modern ears. I have changed the default to 5 (Equal Temperament) and
added information on how to change this at the head of the file.
On a new installation, "Preferences" crashes

On a new (Linux?) installation, if no sound output is enabled, opening "Preferences" crashes.

In mscore/preferences.cpp, mscore/musescore.cpp, mscore/scoreview.cpp seq is accessed but set to 0.

Added some safeguard checks.

(Same for master as another recent patch for qt5)
Merge remote-tracking branch 'origin/master' into AeolusUpdate
Fix #21110 - position the text of glissando according to its physical sizes and no longer by a hard-coded vert. offset

It should also fix #20970: collision of glissando with ledger lines.
Smarter algorithm for avoiding collision with start note ledger line.

Added detection of start note dot(s).
fix tests
Merge pull request #359 from ChurchOrganist/AeolusUpdate

Change Aeolus default to Equal Temperament
Merge pull request #360 from mgavioli/preferences_crash_new_installation

On a new installation, "Preferences" crashes
Improving dot width detection
Merge pull request #367 from mgavioli/Fix_21110_gliss_text_on_wavy_line

Fix #21110 - text on glissando wavy line