Overhaul of dumpstate (aka bugreport) with cleanups & enhancements:

- include basic build & timestamp information in the header
- collect stack traces immediately at bugreport time
- *also* show stack traces from last ANR (as before), if in the last 15 minutes
- alphabetize system properties dump
- remove now-obsolete (and always questionable) "dumpcrash" functionality
- write to a .tmp file first, then rename to the final filename
- friendly usage message
- output sections include the exact file/command run
- source de-weirdification -- it's several hundred lines shorter now

The same data is present in the same order as before, and I've tried
to preserve all the grep/search targets people might use to find their
way through the file.