Test fixes and rebase problems

Note that this removes a number of run-pass tests which are exercising behavior
of the old runtime. This functionality no longer exists and is thoroughly tested
inside of libgreen and libnative. There isn't really the notion of "starting the
runtime" any more. The major notion now is "bootstrapping the initial task".

src/libsyntax/ext/build.rs

@@ -606,7 +606,6 @@ impl AstBuilder for @ExtCtxt {
             ~[
                 self.ident_of("std"),
                 self.ident_of("rt"),
-                self.ident_of("task"),
                 self.ident_of("begin_unwind"),
             ],
             ~[