Bug 799189 - Use mozprocess in cl.py; r=mshal
Bug 905824 - Handle symlinks when validating build environment; r=ted
Bug 907902 - Create system isolated virtualenv, remove --system-ply support; r=glandium
Bug 911375 - Part 2: Convert uses of PurgeManifest to InstallManifest; r=glandium
Bug 911375 - Part 3: Remove PurgeManifest; r=glandium
Bug 911375 - Part 2b: Restore removed make rules necessary for PGO builds; r=bustage
Backout 312925464acb:f24d5b2801f8 (bug 911375) for breaking the build
Merge mozilla-central into build-system