[Tagging] More granular tagging of airports

[John Smith]

For those that missed the email that came up on talk this week,
someone has imported a lot of airports and so on for NZ and it looks
horrible because they show at z10:

http://www.openstreetmap.org/?lat=-37.243&lon=175.014&zoom=10&layers=M

Looking through the wiki I found this proposal:

http://wiki.openstreetmap.org/wiki/Proposed_features/Aerodrome_(unified_symbol_set)

It even has some nice icons already, although I don't a map icon sizes
(about 20px) they could be easily distinguished.

thoughts?