(PhAudio) Display PortAudio overflow/underflow debugging info

Audio input overflows (or underflows for output) are really bad
for LTC syncing. Enable debug messages by setting logMask to 1<<21.

Note: it could be interesting to count the number of overflows and
display the result somewhere in the interface to help the user diagnose
sync failures.
Fix audio input for LTC sync on Windows

Use 16 bits input instead of 8 bits (8-bits setting always returns
samples whose value is zero on Windows).

Ask for a reasonable latency (Asking for zero latency enables an
internal buffering in portaudio at the level of 2 or 3 samples,
and leads to permanent overflow), and read the data in 512-samples
buffers.

In the long run, ideally, decoding the LTC data inside the PortAudio
callback should be avoided to prevent audio overflows. Instead the
callback should simply push the data to a ringbuffer, which should
be decoded in another thread.
Merge pull request #211 from tlecomte/tlWindowsLTC

Windows LTC