https://bugzilla.mozilla.org/show_bug.cgi?id=947125
Actually, while the windows version works better, it is screwed too,
specially on unusually paper sizes and margins.
The main problem with "letter" is, that the gtk code part can't
understand ps paper names, and the ps paper names doesn't unders
Well the whole situation is very complex, the other platform code is more or
less broken too.
Bug 629500 sums the whole situation quite good and looks like a welcome
refactor of the whole code base, maybe it will land in the next years? Feels
like gecko/firefox printing is stuck in IE6 age...
