* Add extra debug messages to the alsa back end to diagnose strange DACs.
* Add configuration file for the `libao` back end -- to change the buffer size and the latency offset, same as for stdout.
* Add `shairport-sync.exe` to `.gitignore`.
-* Add a check to see if compilation is for a CYGWIN platform.
+* Add a check to support compilation on a CYGWIN platform.
* Add `rtptime` tags to metadata and picture information and add two new metadata items to precede and follow the transmission of a picture. Background: it seems that metadata and picture information for the same item, e.g. a track, are normally tagged with a timestamp called the `rtptime`; if they refer to the same item, they will have the same `rtptime` tags. The update here is to add the `rtptime` value, if available, as data to the `mdst` and `mden` metadata items, which are sent before ("MetaData STart") and after ("MetaData ENd") a metadata sequence.
In addition, similar tags -- `pcst` ("PiCture STart") and `pcen` ("PiCture ENd") are now sent before and after a picture with the `rtptime` value, if available, sent as data.
By the way, the progress metadata (`prgr` for "PRoGRess"), which is sent just when a track starts, contains the same `rtptime` as its middle element.