[stdlib] Change C-style for loop to Swift-style for-in loop

[johnlui]

All changes are in one commit now, and it has been fully tested with no "C-style for loop" compiler warnings. @moiseev #826

[johnlui]

also #742

[moiseev]

Thanks @johnlui 👍

@nadavrot , you wanted to postpone merging this in (#742 (comment)) are we good now?

[ephemer]

Is there an official style guide regarding these loops?
I find it easier to read when it's in the style of for i in 0 ..< 8 (with that spacing)

[dabrahams]

There’s no official guide. I will say that the standard library should remain internally consistent, I don’t see any compelling reason to change what we’re doing with range operator spacing.

[ephemer]

Re: internal consistency, the C-style formatting is also spaced in the way I suggested (it's not var i=0; i<8; i+=1).

Comparing 0..<3 and 0 ..< 3, I find the latter significantly easier to process in every case.
The decision ultimately doesn't affect my life in any way, but being an open forum, I wanted to put my vote in for readability.

[moiseev]

Nice catch, @hmhv!
@johnlui please fix the 2 instances of using continue to incremenent loop variable.
For the lack of better way of doing it, here are screenshots.

[johnlui]

@moiseev OK, I will make a new pull request~

[johnlui]

There is a bug-fixed PR #923 , so this will be closed.