Aleks told me all I had to do in order to export net_xp_file.h on the mac was to include it in mozilla/network/main/manifest. I did that, so, if mac builds break in netlib, it's likely the exporting of the file isn't happening (I'm not sure of the state of manifest files anymore) and I don't have a mac. So if MAC BREAKS, please add the file to the mac project and check it in (thank you).
I'll be at 408.867.2701 or cell - 415.307.7101 tonight.