Bug 845089 - Followup: Handle Windows paths when detecting external source directories; r=khuey

This is related to work that landed in part 20 of bug 784841.
Bug 846519 - Running bootstrap.py throws a "NameError: global name HOMEBREW_PACKAGES is not defined" error. r=gps DONTBUILD (NPOTB)
Bug 846463 - Android Nightlies fail to build due to missing /services/sync/locales/Makefile. r=gps
Merge inbound to m-c.
Merge m-c to inbound.