auto merge of #10528 : alexcrichton/rust/static-linking-v2, r=pcwalton

In this series of commits, I've implemented static linking for rust. The scheme I implemented was the same as my [mailing list post](https://mail.mozilla.org/pipermail/rust-dev/2013-November/006686.html).

The commits have more details to the nitty gritty of what went on. I've rebased this on top of my native mutex pull request (#10479), but I imagine that it will land before this lands, I just wanted to pre-emptively get all the rebase conflicts out of the way (becuase this is reorganizing building librustrt as well).

Some contentious points I want to make sure are all good:

* I've added more "compiler chooses a default" behavior than I would like, I want to make sure that this is all very clearly outlined in the code, and if not I would like to remove behavior or make it clearer.
* I want to make sure that the new "fancy suite" tests are ok (using make/python instead of another rust crate)

If we do indeed pursue this, I would be more than willing to write up a document describing how linking in rust works. I believe that this behavior should be very understandable, and the compiler should never hinder someone just because linking is a little fuzzy.

src/librustdoc/lib.rs

@@ -16,7 +16,8 @@
 
 #[desc = "rustdoc, the Rust documentation extractor"];
 #[license = "MIT/ASL2"];
-#[crate_type = "lib"];
+#[crate_type = "lib"]; // NOTE: remove after stage0 snapshot
+#[crate_type = "dylib"];
 
 #[feature(globs, struct_variant, managed_boxes)];