Remove lots of dated configuration from this repo

Remove lots of dated configuration from this repo

Lots of data build stuff is still here from awhile ago when this repo was
producing Cargo binaries, but the rust-lang/rust repo is now responsible for all
these binaries and build configurations. We no longer need to produce artifacts
or have tons of cross-compiles as rust-lang/rust does all that work, instead
let's just test the likely-to-regress platforms and have rust-lang/rust take
care of the rest.

This commit:

* Deletes the old `configure` script and `Makefile`
* Rewrites `src/doc` management as a shell script
* Trims down Travis/AppVeyor configuration