Remove ArtCode.

- Instead use OatQuickMethodHeader.
- Various cleanups now that we don't have all those
  ArtMethod -> ArtCode -> OatQuickMethodHeader indirections.

As a consequence of this cleanup, exception handling got a bit
faster.

ParserCombinators benchmark (exception intensive) on x64: (lower is better)
Before:
ParserCombinators(RunTime): 1062500.0 us.
After:
ParserCombinators(RunTime): 833000.0 us.

Change-Id: Idac917b6f1b0dc254ad68fb3781cd61bccadb0f3
diff --git a/compiler/linker/arm64/relative_patcher_arm64.cc b/compiler/linker/arm64/relative_patcher_arm64.cc
index 6b9c530..6f234a8 100644
--- a/compiler/linker/arm64/relative_patcher_arm64.cc
+++ b/compiler/linker/arm64/relative_patcher_arm64.cc
@@ -22,6 +22,7 @@
 #include "driver/compiler_driver.h"
 #include "utils/arm64/assembler_arm64.h"
 #include "oat.h"
+#include "oat_quick_method_header.h"
 #include "output_stream.h"
 
 namespace art {