Native bindings to the SOFT_source_length extension.

This extension adds a method to retrieve the total length of a source's buffer data in bytes, samples, and seconds, which correspond to the byte, sample, and seconds offset extents. By default, OpenAL only provides a way to retrieve a buffer's storage size in bytes, which does not necessarily represent the data size given to alBufferData nor the byte offset extent for the source's BYTE_OFFSET property. The AL_SOFT_buffer_samples extension allows an application to query a buffer for its length in bytes, samples, and seconds, but this is only for a single buffer; a buffer queue on a source still requires additional bookkeeping by the application to keep track of the length of each buffer being queued and unqueued on a given source. This extension aims to ease that and provide a simple query.