Ignore masked versions

[thesamesam]

A package list with:

...
dev-util/xdelta
...

led to Nattka commenting:

Unable to check for sanity:
> package masked: dev-util/xdelta-3.1.0

In the tree, only >=dev-util/xdelta-3.1.0 is masked.

There's a risk of keywords being lost upon unmasking but I'd prefer Nattka to interpret this as 'the latest non-masked version' to save me needing to manually input a < which may become stale. Perhaps a warning should be emitted re the risk of dropping on unmask.

[mgorny]

I don't know. There might be some piece in the logic chain that will select the wrong version.