flac++.pc.in: Make flac a private requires

Patch pulled from Debian package.

Description:
Chain::Status::as_cstring uses FLAC__Metadata_ChainStatusString which
is in libFLAC. Since the function is inline, every program calling
this function must also link with -lflac, but this is missing in
flac++.pc.

Bug-Debian: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=713645
1 file changed