Use libspotify 12.1.64 for iOS

Change-Id: I29bc66aefc29bdd55abbb490f3ac38b6e3682ae5
SPSession: Maximum event prod timeout of 5.0 seconds

This is somewhat horrible way of alleviating GitHub issue #140 until it can be fixed in libspotify itself.

Change-Id: I66958acbae31c8216e148db8e2c9bd66e27b4fe7
Update versions and documentation for 2.4.4

Change-Id: I69513b4a77222fb7cbe7f024ac8949cd755fe7b4
Update changelog for 2.4.4 release

Change-Id: I128e4d883fa9ecb358b6337973d3e0505850d735
Merge branch 'libspotify-12.1.64' for 2.4.4 release