Some small changes for consistency

[Kimundi]

• Methodyfied the string ascii extionsion functions - They got added recently, I wrapped them in a trait.
• Added into_owned() method for vectors - similar to Str's into_owned() function, allows to convert to a owned vector without making a copy if the source is a owned vector.
• Added or_some method to option - similar to unwrap_or_default, but keeps the values wrapped in an Option. Useful for Option chains, eg Iterator impls.
• Added DoubleEndedIterator impl to Option - Just for compatibility with generic Iterator functions.
• Renamed nil.rs to unit.rs - the type got renamed ages ago, it's time the source file is as well.

[bluss]

.or_some(x) is the same as .or(Some(x)); since the methods are not next to each other in the file, I think you didn't know the latter method.

[bluss]

this pub is redundant and soon to be an error(?)

[Kimundi]

Ah, yeah that is a leftover that I accidentally commited. Is the new rule that no visibility modifiers are allowed inside trait declarations?

[Kimundi]

@blake2-ppc: or_some(x) being the same as or(Some(x)) was kinda the idea... I don't really have a better justification for adding it other than 'people on irc liked the idea of having a function with that semantic a few days ago'. I was discussing unwrap_or_default, and noticed that you could just factor out the unwrap part: or_default().unwrap(). And then I renamed -default to some because that is what it is.

It's like take_unwrap: A convenience method so that you don't need to write as much characters for doing the same thing.

[Kimundi]

Link to IRC snipped that motivated or_some: https://botbot.me/mozilla/rust/msg/5115035/

[Kimundi]

After some discussion on IRC I removed the or_some() method for now because it was not clear if it is needed.