First draft of the sh4 port

src/platform.h

Index: src/platform.h
diff --git a/src/platform.h b/src/platform.h
index 2ac63ff729540f045e09cbb5769480643becea76..e6792d8afa9965301be2f8585874a60d80469df7 100644
--- a/src/platform.h
+++ b/src/platform.h
@@ -321,6 +321,9 @@ class OS {
   // Support runtime detection of FPU on MIPS CPUs.
   static bool MipsCpuHasFeature(CpuFeature feature);
 
+  // Support runtime detection of features on SH CPUs.
+  static bool SHCpuHasFeature(CpuFeature feature);
+
   // Returns the activation frame alignment constraint or zero if
   // the platform doesn't care. Guaranteed to be a power of two.
   static int ActivationFrameAlignment();