Bug 1061251 - Fix more bad implicit constructors in accessible; r=tbsaunde
Bug 1061009 - Fix more bad implicit constructors in a11y; r=tbsaunde
Bug 1061047 - Fix some bad implicit constructors in imagelib; r=jrmuizel
Bug 1060918 - Do not rely on two implicit conversions in GLContextProviderWGL.cpp for clang-cl compatibility; r=jrmuizel

This works around http://llvm.org/PR20821.