support/scripts/pkg-stats: add column reporting ignored CVEs

support/scripts/pkg-stats: add column reporting ignored CVEs

When doing analysis it is helpful to be able to view what CVE have
been patched / diagnosed to not apply to Buildroot. This exposes
that list to the reporting and prevents a step where you have to
dig into the .mk's of a pkg to check for sure what has been
ignored.

Signed-off-by: Matthew Weber <matthew.weber@rockwellcollins.com>
[yann.morin.1998@free.fr: only set background if there are ignored CVEs]
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>