Move the dataflow framework to its own crate.

Author: cjgillot

src/base.rs

@@ -23,7 +23,7 @@ pub(crate) fn codegen_fn<'tcx>(
     let mir = tcx.instance_mir(instance.def);
     let _mir_guard = crate::PrintOnPanic(|| {
         let mut buf = Vec::new();
-        rustc_mir::util::write_mir_pretty(tcx, Some(instance.def_id()), &mut buf).unwrap();
+        rustc_middle::mir::write_mir_pretty(tcx, Some(instance.def_id()), &mut buf).unwrap();
         String::from_utf8_lossy(&buf).into_owned()
     });
 

src/lib.rs

@@ -16,7 +16,6 @@ extern crate rustc_incremental;
 extern crate rustc_index;
 extern crate rustc_interface;
 extern crate rustc_metadata;
-extern crate rustc_mir;
 extern crate rustc_session;
 extern crate rustc_span;
 extern crate rustc_target;