Proper solution to replace 9cabc1b hack.

Initialize uninitialized variable (m_started), remove cruft.

libs/backends/portaudio/winmmemidi_input_device.cc

@@ -37,6 +37,7 @@ namespace ARDOUR {
 
 WinMMEMidiInputDevice::WinMMEMidiInputDevice (int index)
 	: m_handle(0)
+	, m_started(false)
 	, m_midi_buffer(new RingBuffer<uint8_t>(MIDI_BUFFER_SIZE))
 	, m_sysex_buffer(new uint8_t[SYSEX_BUFFER_SIZE])
 {

libs/backends/portaudio/winmmemidi_input_device.h

@@ -91,7 +91,6 @@ private: // data
 	MIDIHDR m_sysex_header;
 
 	bool m_started;
-	bool m_enabled;
 
 	std::string m_name;
 

libs/backends/portaudio/wscript

@@ -40,6 +40,3 @@ def build(bld):
                    'ARDOURBACKEND_DLL_EXPORTS',
                    'USE_MMCSS_THREAD_PRIORITIES'
                   ]
-    if bld.env['build_target'] == 'mingw':
-        # MIDI input doesn't work with -O3 or -O2 so override
-        obj.cxxflags = [ '-O0' ]