auto merge of #19070 : nikomatsakis/rust/crates, r=nikomatsakis

Reduces memory usage significantly and opens opportunities for more parallel compilation.

This PR was previously #19002 but I closed it because bors didn't seem to recognize the `r+` annotations there.

src/librustdoc/lib.rs

@@ -22,6 +22,7 @@ extern crate arena;
 extern crate getopts;
 extern crate libc;
 extern crate rustc;
+extern crate rustc_trans;
 extern crate serialize;
 extern crate syntax;
 extern crate "test" as testing;
@@ -155,7 +156,7 @@ pub fn main_args(args: &[String]) -> int {
         usage(args[0].as_slice());
         return 0;
     } else if matches.opt_present("version") {
-        match rustc::driver::version("rustdoc", &matches) {
+        match rustc_trans::driver::version("rustdoc", &matches) {
             Some(err) => {
                 println!("{}", err);
                 return 1