Refactor the compilers out of libart.

This builds three separate compilers and dynamically links with the right one
at runtime.

Change-Id: I59d22b9884f41de733c09f97e29ee290236d5f4b
diff --git a/src/compiler/codegen/CodegenFactory.cc b/src/compiler/codegen/CodegenFactory.cc
index b27efe0..8a6e1bc 100644
--- a/src/compiler/codegen/CodegenFactory.cc
+++ b/src/compiler/codegen/CodegenFactory.cc
@@ -266,7 +266,7 @@
 }
 
 /*
- * Utiltiy to load the current Method*.  Broken out
+ * Utility to load the current Method*.  Broken out
  * to allow easy change between placing the current Method* in a
  * dedicated register or its home location in the frame.
  */