Rename OatCompilationUnit to Dex.. move to compiler.

Some other clean-up to make fields const and private.

Change-Id: Icad66e2969385ab1f4125162bcbf8d5fa92d3ed5
diff --git a/src/compiler/dex/compiler_ir.h b/src/compiler/dex/compiler_ir.h
index 04dee77..76e838c 100644
--- a/src/compiler/dex/compiler_ir.h
+++ b/src/compiler/dex/compiler_ir.h
@@ -20,8 +20,8 @@
 #include <vector>
 #include "dex_instruction.h"
 #include "compiler/driver/compiler_driver.h"
+#include "compiler/driver/dex_compilation_unit.h"
 #include "compiler_utility.h"
-#include "oat_compilation_unit.h"
 #include "safe_map.h"
 #include "compiler_llvm/ir_builder.h"
 #include "compiler_llvm/intrinsic_helper.h"