Add a utils::join() function to join elements of a container into a
string, with a separator and an optional conversion function if the
elements are not implicitly convertible to std::string.
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>
Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>