Parse the creation date out of uploaded audio files

[desrosj]

This is a companion ticket to #35218 which adds parsing for the creation date out of uploaded video files, and will introduce wp_get_media_creation_timestamp().

The same should be done for audio files using the same function.

I uploaded a handful of test files to a site and debugged the raw ID3 data. Here is what that turned up:

MP3, FLAC:

None of these had anything like a file creation timestamp, only meta related to the recording like "year".

MPC:

ID3 error: Format not supported, module "module.audio.mpc.php" was removed.

MP4:

This is stored exactly like MP4 video: $metadata['quicktime']['moov']['subatoms']['0']['creation_time_unix']

WMA:

Works just like video "asf": $metadata['asf']['file_properties_object']['creation_date_unix']

Parse WMA files fir creation date.

Test WMA file.

In 42017.patch​ I added the same approach used in wp_read_video_metadata() to wp_read_audio_metadata() (see r41746). Also attached is a test file that should go in the tests/phpunit/data/uploads/ directory.

I talked this over with @blobfolio. The only other file type that may be worth checking is an AAC (Apple audio). I will run some tests on that format when I get a chance.

Looks like the wp-includes/ID3/module.audio-video-asf.php file has an anonymous function in it, so the tests do not pass on PHP 5.2 (​https://travis-ci.org/desrosj/wordpress-develop/builds/284383012).