Adding various string and vector functions

[killerswan]

These commits add the following:

• str::map
• str::all (aka loop_chars)
• str::any
• str::bytes_iter
• str::chars_iter (aka iter_chars)
• str::words_iter
• str::lines_iter
• str::windowed
• vec::windowed
• (NEW) str::from_bytes (UTF-8 safe)

[kud1ing]

Cool, that was on my wishlist for a while.

[kud1ing]

And once @nikomatsakis commits his to_list() we should switch the string functions to iteration-only and get rid of the duplication.

See https://mail.mozilla.org/pipermail/rust-dev/2012-January/001216.html

[nikomatsakis]

Can you change the block types in the parameter lists from fn&() to fn()?

[killerswan]

How's this?

[nikomatsakis]

Merged as 477c3a8 ... 69ffb4e