Find a way to unwind through .qmlc and .jsc files

We can already unwind by frame pointer to retrieve raw instruction pointer addresses from sections of stack in those files. If there was some way to retrieve the QML/JS function names, based on those, that would be really great.

Also, the frame pointer fallbacks in elfutils are somewhat ugly as they can duplicate frames sometimes and they can mess up the unwinding of dwarf data underneath the frame-pointer unwound sections by "forgetting" register values. So, if we could avoid the frame pointer unwinding altogether and restore a proper set of registers after unwinding through QML/JS that would be nice.