Implement consuming iterators for ~[], remove vec::{consume, consume_reverse, map_consume}.
Remove vec::{filter, filtered, filter_map, filter_mapped}, replaced by iterators.
Remove vec::reversed, replaced by iterators.
Remove standalone comparison functions in vec, make the trait impls better.
Convert vec::{split, splitn, rsplit, rsplitn} to external iterators.
Convert vec::windowed to an external iterator, and add an n-at-a-time chunk iterator.
Convert vec::{as_imm_buf, as_mut_buf} to methods.
auto merge of #7566 : huonw/rust/vec-kill, r=cmr

The last remaining internal iterator in `vec` is `each_permutation`.