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/ralloc_util.cc b/compiler/dex/quick/ralloc_util.cc
index 0a98c80..8efafb2 100644
--- a/compiler/dex/quick/ralloc_util.cc
+++ b/compiler/dex/quick/ralloc_util.cc
@@ -16,10 +16,13 @@
 
 /* This file contains register alloction support. */
 
-#include "dex/compiler_ir.h"
-#include "dex/compiler_internals.h"
 #include "mir_to_lir-inl.h"
 
+#include "dex/compiler_ir.h"
+#include "dex/mir_graph.h"
+#include "driver/compiler_driver.h"
+#include "driver/dex_compilation_unit.h"
+
 namespace art {
 
 /*