RFC: complete set of vector types

[graydon]

https://mail.mozilla.org/pipermail/rust-dev/2012-March/001467.html with the slight revision to syntax shown at the beginning of https://mail.mozilla.org/pipermail/rust-dev/2012-March/001476.html

I actually don't care too much about syntax on this -- anything that looks ok is fine -- I just want to get the semantics worked out and implemented. Any objections? I'm starting to prototype this in my own repo presently.

[pcwalton]

Extremely excited to see progress! No objections here.

[graydon]

WIP branch for this: https://github.com/graydon/rust/tree/evecs

[graydon]

I think this is done enough to close this bug; sub-bugs for specific missing features are fine.