wasapi: first stab of audio output using the Windows Audio Session API

This is _very_ incomplete and buggy:
 - no time synchronization,
 - no sample format, sample rate and channels mask negotiation,
 - no channels reordering,
 - no S/PDIF and HDMI pass-through,
 - no volume control,
 - no device selection,
 - no fail-over to another device when needed,
 - leaking COM thread data at exit (missing dedicated thread),
 - incomplete build system integration.

But it compiles (with mingw-w64) and outputs working audio.

modules/audio_output/Modules.am

@@ -45,6 +45,12 @@ if HAVE_PULSE
 libvlc_LTLIBRARIES += libpulse_plugin.la
 endif
 
+libwasapi_plugin_la_SOURCES = wasapi.c
+libwasapi_plugin_la_CFLAGS = $(AM_CFLAGS)
+libwasapi_plugin_la_LIBADD = $(AM_LIBADD) -lole32 -lksuser
+libwasapi_plugin_la_DEPENDENCIES =
+EXTRA_LTLIBRARIES += libwasapi_plugin.la
+
 libkai_plugin_la_SOURCES = kai.c packet.c
 libkai_plugin_la_CFLAGS = $(AM_CFLAGS)
 libkai_plugin_la_LIBADD = $(AM_LIBADD) $(KAI_LIBS)