Include stddef.h instead of stdlib.h for size_t definition.

Change-Id: Id3fa2dff0279985ca865caf7e3dfa7b4e77ee345
diff --git a/vm/alloc/Alloc.h b/vm/alloc/Alloc.h
index facc753..8532a97 100644
--- a/vm/alloc/Alloc.h
+++ b/vm/alloc/Alloc.h
@@ -19,7 +19,7 @@
 #ifndef _DALVIK_ALLOC_ALLOC
 #define _DALVIK_ALLOC_ALLOC
 
-#include <stdlib.h>
+#include <stddef.h>
 
 /*
  * Initialization.