Bug 818246 - Part 3: Build system support for XPIDLSRCS in moz.build; r=glandium
Bug 818246 - Part 4: Move XPIDLSRCS into moz.build (auto); rs=glandium

This is the result of running
|mach mozbuild-migrate --list XPIDLSRCS SDK_XPIDLSRCS XPIDL_SOURCES| and
reverting xpcom/sample/*.
Bug 818246 - Part 5: Move XPIDLSRCS into moz.build (manual); r=glandium
Bug 818246 - Part 6: Support XPIDL_MODULE in moz.build; r=gps
Bug 818246 - Part 7: Move XPIDL_MODULE to moz.build; rs=gps
Bug 818246 - Part 8: Support XPIDL_FLAGS in moz.build; r=gps
Bug 818246 - Part 9: Move XPIDL_FLAGS to moz.build; r=gps
Merge mozilla-central into build-system

dom/interfaces/svg/Makefile.in and dom/media/Makefile.in had merge
conflicts. They were resolved by hand. The former needed 2 IDLs removed.
The latter had a context conflict for EXPORTS_NAMESPACES.
Merge mozilla-central into build-system