set MaxNativeCallFootprint to 5 on 32-bit systems

Thunks such as divideLong now take a pointer and two int64_t
arguments, which amounts to 5 words of stack space on a 32-bit system.

src/compile.cpp

@@ -52,7 +52,7 @@ const bool Continuations = true;
 const bool Continuations = false;
 #endif
 
-const unsigned MaxNativeCallFootprint = 4;
+const unsigned MaxNativeCallFootprint = BytesPerWord == 8 ? 4 : 5;
 
 const unsigned InitialZoneCapacityInBytes = 64 * 1024;