fixed UnwrapThrowExt formatting to align with core

[jquesada2016]

This pull request closes #2732

[alexcrichton]

I believe it was originally intended that the E was ignored since the purpose of using these methods was to avoid the panicking infrastructure and have a lightweight cost in terms of code size. Additionally these methods are also somewhat broken where destructors for values on the stack are not run yet the instance can still be reentered. This isn't actually memory safe in Rust and is a long outstanding but in wasm-bindgen.

[jquesada2016]

I do get the desire to shave off the baggage that comes with the panicking infrastructure, but it is very useful and makes debugging much more painful then it needs to be.

How about feature gating this?

Also, since the E is ignored, it would also be prudent to drop the E: Debug constraint.

Edit:
Nevermind, I forgot for a moment this has the original behavior on non-wasm targets.

[alexcrichton]

GIven the type bounds in play I think I'd prefer to keep this as-is and avoid the complication of feature gating and such. This is just a trait implementation so it's always possible to do something else externally as well.