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/driver/compiler_driver-inl.h b/compiler/driver/compiler_driver-inl.h
index 022ec6b..4d5d253 100644
--- a/compiler/driver/compiler_driver-inl.h
+++ b/compiler/driver/compiler_driver-inl.h
@@ -20,6 +20,7 @@
 #include "compiler_driver.h"
 
 #include "dex/compiler_ir.h"
+#include "dex_compilation_unit.h"
 #include "field_helper.h"
 #include "mirror/art_field-inl.h"
 #include "mirror/art_method-inl.h"