Implement unaligned allocate and allocate heap numbers in runtime double unaligned.

src/globals.h

Index: src/globals.h
diff --git a/src/globals.h b/src/globals.h
index 5b6aa26665b6744706d652061f9a2a546b9b76ec..00623ca7056b596241edfcded577b0cb235e9eb3 100644
--- a/src/globals.h
+++ b/src/globals.h
@@ -438,6 +438,7 @@ enum AllocationSpace {
 const int kSpaceTagSize = 3;
 const int kSpaceTagMask = (1 << kSpaceTagSize) - 1;
 
+enum AllocationAlignment { kWordAligned, kDoubleAligned, kDoubleUnaligned };
 
 // A flag that indicates whether objects should be pretenured when
 // allocated (allocated directly into the old generation) or not