Add buffer properties to get the internal format, and the length in bytes, samples...

Add buffer properties to get the internal format, and the length in bytes, samples, and seconds

The provided buffer lengths correspond to the source offsets, in that the byte
length specifies the end of the byte offset (ie, when the buffer is used for a
static source, the offset will range between 0 (inclusive) and the byte length
(exclusive)). Although an application could use the AL_SIZE, AL_CHANNELS,
AL_BITS, and AL_FREQUENCY properties to find the length in samples and seconds,
the byte length cannot be reliably calculated this way.