Windows and Mac, and fix a couple nsSpecialSystemDirectory bugs.
All the changes are BeOS specific (i.e. wrapped in XP_BEOS or
only used by code wrapped in XP_BEOS).
r=mcafee
git-svn-id: svn://10.0.0.236/trunk@57190 18797224-902f-48f8-a5cc-f745e15eee43