Subzero. ARM32. Combine allocas.

BUG= https://code.google.com/p/nativeclient/issues/detail?id=4076
R=stichnot@chromium.org

Review URL: https://codereview.chromium.org/1465213002 .
diff --git a/src/IceTargetLowering.h b/src/IceTargetLowering.h
index 1350afa..bac403f 100644
--- a/src/IceTargetLowering.h
+++ b/src/IceTargetLowering.h
@@ -211,6 +211,7 @@
   virtual uint32_t getStackAlignment() const = 0;
   virtual void reserveFixedAllocaArea(size_t Size, size_t Align) = 0;
   virtual int32_t getFrameFixedAllocaOffset() const = 0;
+  virtual uint32_t maxOutArgsSizeBytes() const { return 0; }
 
   /// Return whether a 64-bit Variable should be split into a Variable64On32.
   virtual bool shouldSplitToVariable64On32(Type Ty) const = 0;