[pca] patch factor

[Martin Paul]

Hi,

The current development release of pca contains two new (numerical) 
fields in the header:

   $ pca
   ...
   List: missing (227/22563)
   ...

The first number (227) is the number of patches listed. The second 
(22563) is the sum of all patch ages (in days, the "Age" column) which 
can be used as a very simple summary about the current state of missing 
patches. The higher the number, the longer the machine has not been patched.

I'm the first to admit that there are several reasons why a single 
number can never be an exact interpretation of how a machine is being 
kept up to date, but it's a quick way to determine machines which 
deserve a closer look.

Martin.