Move EntityList and SparseMap into the entity module.

These data structures are dependent on EntityRef and EntityMap, so it
makes sense to keep them in the same module.

lib/cretonne/src/regalloc/liverange.rs

@@ -107,10 +107,10 @@
 //! of coalescing, so we would need to roll our own.
 //!
 
-use std::cmp::Ordering;
+use entity::SparseMapValue;
 use ir::{Inst, Ebb, Value, ProgramPoint, ExpandedProgramPoint, ProgramOrder};
 use regalloc::affinity::Affinity;
-use sparse_map::SparseMapValue;
+use std::cmp::Ordering;
 
 /// Global live range of a single SSA value.
 ///