AsyncRead: Some issues with default error type having lifetime.

[cheako]

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The easy part to fix is to add some documentation about nom-bufreader, if you want an issue to track this it's #810 Some work in nom would be nice regarding https://github.com/rust-bakery/nom-bufreader/issues/9 It seems there is reason to add .to_owned() or something to nom's error type. I've been forcing () in for E, as in IResult<&[u8], Self, ()>.

[WhyNotHugo]

I've a different scenario where .to_owned() would also be useful: I have a function that runs an external command, parses the stdout and returns the parsed output.

In case of error, I return a custom error type of mine, but I'd like to wrap around the original error returned by nom. The to_owned method would allow me to return the error.