Bug 915928 - Remove toolkit/Makefile.in. r=khuey
Bug 917622 - Use INSTALL_TARGETS for mochitests. r=gps
Bug 910453 - Annotate read moz.build files with tier info. r=glandium
Bug 917086 - Disallow DIRS, PARALLEL_DIRS and TEST_DIRS under TOOL_DIRS and TEST_TOOL_DIRS, and adapt moz.build files accordingly. r=gps

Also mark TOOL_DIRS/TEST_TOOL_DIRS directories in backend.mk and recurse them normally instead of forcing make -C dir libs for them.