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/entrypoints/interpreter/interpreter_entrypoints.cc b/runtime/entrypoints/interpreter/interpreter_entrypoints.cc
index b617636..908d3cd 100644
--- a/runtime/entrypoints/interpreter/interpreter_entrypoints.cc
+++ b/runtime/entrypoints/interpreter/interpreter_entrypoints.cc
@@ -25,7 +25,7 @@
 namespace art {
 
 // TODO: Make the MethodHelper here be compaction safe.
-extern "C" void artInterpreterToCompiledCodeBridge(Thread* self, MethodHelper& mh,
+extern "C" void artInterpreterToCompiledCodeBridge(Thread* self, MethodHelper* mh,
                                                    const DexFile::CodeItem* code_item,
                                                    ShadowFrame* shadow_frame, JValue* result) {
   mirror::ArtMethod* method = shadow_frame->GetMethod();
@@ -54,7 +54,7 @@
   } else {
     method->Invoke(self, shadow_frame->GetVRegArgs(arg_offset),
                    (shadow_frame->NumberOfVRegs() - arg_offset) * sizeof(uint32_t),
-                   result, mh.GetShorty());
+                   result, mh->GetShorty());
   }
 }