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/mips/assemble_mips.cc b/compiler/dex/quick/mips/assemble_mips.cc
index 4265ae1..a531317 100644
--- a/compiler/dex/quick/mips/assemble_mips.cc
+++ b/compiler/dex/quick/mips/assemble_mips.cc
@@ -16,7 +16,9 @@
 
 #include "codegen_mips.h"
 
-#include "dex/quick/mir_to_lir-inl.h"
+#include "base/logging.h"
+#include "dex/compiler_ir.h"
+#include "dex/quick/mir_to_lir.h"
 #include "mips_lir.h"
 
 namespace art {