FLAC decoder (and a playsound.c bug)

[Ryan C. Gordon]

> I'm going to go install libFLAC and then I'll commit the flac module, too.

...and commit I did.

I fixed one thing in the decoder (strcmp(magic, "fLaC") was comparing
against a non-null terminated buffer), and it seems to work well here. I
also managed to scratch out the configure.in entry for it.  :)

Also, finally, I switched the CHANGELOG to list newest entries first.

--ryan.