ao_wasapi: make code shorter

Also fix a format string mistake in a log call using it.

I wonder if this code shouldn't use FormatMessage, but it looks kind
of involved [1], so: no, thanks.

[1] http://support.microsoft.com/kb/256348/en-us
player: add missing "-" to options in workaround notice on A/V desynchronization

While it technically works, using GNU-style options seems cleaner nowadays.

Signed-off-by: wm4 <wm4@nowhere>