ART: Clean up compiler

Clean up the compiler: less extern functions, dis-entangle
compilers, hide some compiler specifics, lower global includes.

Change-Id: Ibaf88d02505d86994d7845cf0075be5041cc8438
diff --git a/compiler/oat_test.cc b/compiler/oat_test.cc
index 11d1728..28710e0 100644
--- a/compiler/oat_test.cc
+++ b/compiler/oat_test.cc
@@ -14,6 +14,7 @@
  * limitations under the License.
  */
 
+#include "class_linker.h"
 #include "common_compiler_test.h"
 #include "compiler.h"
 #include "dex/verification_results.h"