Add API for serializing back to Apple's crash report format?

[luser]

Thanks for writing this crate, it's super useful! I'm using it to write a little commandline tool to take Apple crash reports from our customers and symbolicate the frames from our framework using our private dSYMs. Ideally I'd like to have it take a crash report file as input and spit out a crash report file, just with the newly-symbolicated frames filled in. Would it be feasible to provide an API to serialize back to Apple's format? If not, some half-measure like a way to map bits of the AppleCrashReport structure back to lines from the input file might be good enough for my purposes.

Currently I'm resorting to parsing the report using this crate so that I can easily find and use the UUID of our framework, then just iterating over the lines of the report and rewriting the frames I care about (which requires only a tiny bit of actual parsing). If I had some way to find all the frames I care about using this crate so I could fill in their symbol data and write it back out that would be wonderful.

[flub]

I guess that could be as simple as aToString/Display impl? I don't think we'd be working on it but I don't see why we wouldn't accept it as a PR>