Add code for CPU feature detection and use it to detect SSE3 and SSE 4.1.

runtime/bin/main.cc

Index: runtime/bin/main.cc
===================================================================
--- runtime/bin/main.cc	(revision 12828)
+++ runtime/bin/main.cc	(working copy)
@@ -655,9 +655,11 @@
   Dart_SetVMFlags(vm_options.count(), vm_options.arguments());
 
   // Initialize the Dart VM.
-  Dart_Initialize(CreateIsolateAndSetup,
-                  NULL,
-                  ShutdownIsolate);
+  if (!Dart_Initialize(CreateIsolateAndSetup,
+                       NULL,
+                       ShutdownIsolate)) {
+    return ErrorExit("VM initialization failed\n");
+  }
 
   DartUtils::SetOriginalWorkingDirectory();