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/x86/int_x86.cc b/compiler/dex/quick/x86/int_x86.cc
index 03156dc..4fe7a43 100755
--- a/compiler/dex/quick/x86/int_x86.cc
+++ b/compiler/dex/quick/x86/int_x86.cc
@@ -17,6 +17,8 @@
 /* This file contains codegen for the X86 ISA */
 
 #include "codegen_x86.h"
+
+#include "base/logging.h"
 #include "dex/quick/mir_to_lir-inl.h"
 #include "dex/reg_storage_eq.h"
 #include "mirror/art_method.h"