do not write control chars in XML
fix #18618 : File suffix has to be entered when saving snapshot
fix #13577 : Drag-selected lasso rectangle remains
fix #19129 : Small note in chord is detached from stem
Merge pull request #244 from Soerboe/fix19129

fix #19129 : Small note in chord is detached from stem
fix bad alignment of small notehead in tablature
Merge pull request #242 from Soerboe/fix18618

fix #18618 : File suffix has to be entered when saving snapshot
Merge pull request #243 from Soerboe/fix13577

fix #13577 : Drag-selected lasso rectangle remains
Fix #19931: Use native file dialog on windows and mac, and qt file dialog on unix