ART: Some Quick cleanup

Make several fields const in CompilationUnit. May benefit some Mir2Lir
code that repeats tests, and in general immutability is good.

Remove compiler_internals.h and refactor some other headers to reduce
overly broad imports (and thus forced recompiles on changes).

Change-Id: I898405907c68923581373b5981d8a85d2e5d185a
diff --git a/compiler/dex/quick/gen_invoke.cc b/compiler/dex/quick/gen_invoke.cc
index d5889f5..bb5b0cd 100755
--- a/compiler/dex/quick/gen_invoke.cc
+++ b/compiler/dex/quick/gen_invoke.cc
@@ -14,12 +14,16 @@
  * limitations under the License.
  */
 
+#include "mir_to_lir-inl.h"
+
 #include "arm/codegen_arm.h"
 #include "dex/compiler_ir.h"
-#include "dex/frontend.h"
+#include "dex/dex_flags.h"
+#include "dex/mir_graph.h"
 #include "dex/quick/dex_file_method_inliner.h"
 #include "dex/quick/dex_file_to_method_inliner_map.h"
 #include "dex_file-inl.h"
+#include "driver/compiler_driver.h"
 #include "entrypoints/quick/quick_entrypoints.h"
 #include "invoke_type.h"
 #include "mirror/array.h"
@@ -27,7 +31,6 @@
 #include "mirror/dex_cache.h"
 #include "mirror/object_array-inl.h"
 #include "mirror/string.h"
-#include "mir_to_lir-inl.h"
 #include "scoped_thread_state_change.h"
 
 namespace art {