fix warnings due to -Wunused-parameter
handle style change for Marker
fix warnings due to -Wunused-variable
fix warnings due to -Wswitch
fix warnings due to -Wparentheses
fix warnings due to -Wunused-function
fix warning reg. "name xxx already in use"

using the names they defaults to
fix error introduced when fixing warnings due to -Wswitch
fix error introduced when fixing warning -Wunused-function
fix cmake warning with cmake >= 2.8.11
fix warnings due to -Wunused-but-set-variable
Fix for issue #24339
Slurs between voices will now save and restore properly.
The MuseScore debugger has not been fixed to display the cross-voice
property of such slurs.
fix 24359: changing "directory" to "folder"
fix #24350: markings lost after timesig change

Annotations were completely lost, spanners placed incorrectly.  Also,
repeat measure symbol caused hang.  These are fixed.  Key signatures
still can get messed up, at least until reload.  And barline styles are
lost even when they coincide.
fix #24359: changing plural to singular
fix 24359: it wasn't just the UI file affected...
fix 23366: more capitalization
add test
Corrected both reading and writing.
A slur is not equivalent to most of the other spanner elements since it
is related to specific voices, not once but twice.
Remove references to "this"