flx: require cl-lib; avoid ugly eval-when-compile

Also prefix various functions with "cl-", and add a Package-Requires
header.

Signed-off-by: Ramkumar Ramachandra <artagnon@gmail.com>
flx-ido: don't require cl; flx requires it anyway

Also prefix various functions with "cl-", and add a Package-Requires
header.

Signed-off-by: Ramkumar Ramachandra <artagnon@gmail.com>