Make ART compile with GCC -O0 again.

Tidy up InstructionSetFeatures so that it has a type hierarchy dependent on
architecture.
Add to instruction_set_test to warn when InstructionSetFeatures don't agree
with ones from system properties, AT_HWCAP and /proc/cpuinfo.
Clean-up class linker entry point logic to not return entry points but to
test whether the passed code is the particular entrypoint. This works around
image trampolines that replicate entrypoints.
Bug: 17993736

Change-Id: I5f4b49e88c3b02a79f9bee04f83395146ed7be23
diff --git a/runtime/mirror/string.h b/runtime/mirror/string.h
index 1320ab7..64408a6 100644
--- a/runtime/mirror/string.h
+++ b/runtime/mirror/string.h
@@ -17,8 +17,6 @@
 #ifndef ART_RUNTIME_MIRROR_STRING_H_
 #define ART_RUNTIME_MIRROR_STRING_H_
 
-#include <gtest/gtest.h>
-
 #include "gc_root.h"
 #include "object.h"
 #include "object_callbacks.h"
@@ -163,7 +161,8 @@
   static GcRoot<Class> java_lang_String_;
 
   friend struct art::StringOffsets;  // for verifying offset information
-  FRIEND_TEST(ObjectTest, StringLength);  // for SetOffset and SetCount
+  ART_FRIEND_TEST(ObjectTest, StringLength);  // for SetOffset and SetCount
+
   DISALLOW_IMPLICIT_CONSTRUCTORS(String);
 };