[phobos] UnbufferedFile, or, abstracting the File ranges

[Lars Tandle Kyllingstad]

In the process of designing std.process it has become obvious, as
pointed out by Steve, that Phobos needs facilities for unbuffered I/O.
To that end, I've started writing an UnbufferedFile type, the current
status of which can be seen here:

        Code: http://github.com/kyllingstad/ltk/blob/master/ltk/stdio.d
        Docs: http://kyllingen.net/code/ltk/doc/stdio.html

(Disclaimer: This is very much a work-in-progress, there's lots of stuff
that needs to be added yet, and I'd be surprised if there wasn't lots of
room for improvement, performance-wise.)


Now, while writing this it has kind of annoyed me that I have to write
new implementations of the byLine and byChunk ranges.  I've personally
found them incredibly useful, so I want them in UnbufferedFile, but the
ones in std.stdio are tailored for File.

I therefore suggest we try to abstract these ranges, so they can operate
on general types that define a set of primitives such as read(), readc()
and readln().

Are there problems with this?  Any comments?

-Lars