Bug 995047.  Change out stack/exception APIs to hand out AString instead of AUTF8String for filename/functionname, so we end up with fewer string conversions in practice.  r=smaug
Bug 994811 part 1.  Add a ToJSValue overload for dictionary types. r=bholley
Bug 994811 part 2.  Use ToJSValue in msMessage::GetDeliveryInfo.  r=gene

There is one behavior change here: the old code converted null strings
in the MmsDeliveryInfo into "", but the new code will convert them to
a JS null value.