This replaces the simple string used by pa_format_info's proplist with a
JSON string (accessed via new API only). This allows us to express lists
and ranges more cleanly, and embed type information for future
extensibility.
We use json-c for JSON parsing. This is a lightweight depdency (32 KB on
my system) and avoids the hassle of having to reinvent a JSON parser.
Also included is a test which verifies functionality and is
valgrind-clean.
IEC61937-encapsulated E-AC3 frames contain 6 audio blocks per substream,
which corresponds to 1536 samples contained a 24576-byte frame. To cope
with this, we maintain the s16le stereo sample spec, but quadruple the
sample rate so that the conversion remains accurate.
We frequently need to free an idxset containing pa_format_infos, so
define an internal free function that can be used directly with this
(instead of defining it once-per-file).
