gecko-dev/third_party/rust/mp4parse_fallible

This is from https://github.com/servo/servo/tree/master/components/fallible
with modificaion for mp4 demuxer.

The purpose of this crate is to solve infallible memory allocation problem
which causes OOM easily on win32. This is more like a temporary solution.
Once rust supports fallible memory allocation in its stdlib, this can be
retired.