Replace libfaac with aac in get_iplayer.cgi?

[Martin Campbell]

In the latest ffmpeg, libfaac is no longer supported. Should references 
to it be replaced with the experimental aac, which is?

In get_iplayer.cgi, replace:
push @cmd_aopts, ( '-acodec', 'libfaac',
with:
push @cmd_aopts, ( '-acodec', 'aac', '-strict', 'experimental',