applemedia: fix makefile typo
applemedia: register iosassetsrc as a primary element
iosassetsrc: use the correct uri when checking for valid uris
ioassetsrc: use ios locking features
iosassetsrc: Retain the asset and assetrepresentation to keep them valid

It seems iOS cleans up the asset resources after the block ends. Need to
explicitly inform it that ioassetsrc wants to keep them around for
longer time
iosassetsrc: use the right buffer pointer when reading data
eaglcontext: only release, do not dealloc

Release only to get rid of our ref to it, instead of forcing a
dealloc
applemedia: fix strides for iOS in coremedia buffers
applemedia: add new source/decoder element for iOS assets