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/arm/arm_lir.h b/compiler/dex/quick/arm/arm_lir.h
index 5d09ae1..9717459 100644
--- a/compiler/dex/quick/arm/arm_lir.h
+++ b/compiler/dex/quick/arm/arm_lir.h
@@ -17,7 +17,9 @@
 #ifndef ART_COMPILER_DEX_QUICK_ARM_ARM_LIR_H_
 #define ART_COMPILER_DEX_QUICK_ARM_ARM_LIR_H_
 
-#include "dex/compiler_internals.h"
+#include "dex/compiler_enums.h"
+#include "dex/reg_location.h"
+#include "dex/reg_storage.h"
 
 namespace art {