Added functionality to query the name of the source port of a MidiEvent
by calling MidiClient::sourcePortName( const MidiEvent & ).
(cherry picked from commit 5ec96a9483)
The MidiClient::writablePorts() method was not overloaded properly in
MidiWinMM implementation due to a typo. This should fix list of output
devices being empty on win32.
(cherry picked from commit 40c56de898)