[pca] Patch blacklist?

[Martin Paul]

> Maybe something like a '--never=' option to avoid breaking the existing syntax?

Adding new more options is the one thing I hate even more than breaking 
existing behaviour :) We'll see - other options are affected as well; 
e.g. when specifying to show only missing security patches (missings), 
non-security patches will show up as well if they are required. Some 
people might not like that, either.

Martin.