Incorrect whitespace check in comment parser

[brson]

comments.rs contains this:

fn all_whitespace(s: ~str, begin: uint, end: uint) -> bool {                                                                                                                                                         
    let mut i: uint = begin;                                                                                                                                                                                         
    while i != end {                                                                                                                                                                                                 
        if !is_whitespace(s[i] as char) { return false; } i += 1u;                                                                                                                                                   
    }                                                                                                                                                                                                                
    return true;                                                                                                                                                                                                     
}    

Doing a bytewise conversion to chars is not right.

[pnkfelix]

Not critical for 0.6; de-milestoning

[catamorphism]

far-future

[brson]

Fixed.