add typecast to avoid (unlikely but possible) integer overflows.

this will silence a lot of static code analysis warnings

src/my_pool_chunk.cpp

@@ -212,10 +212,10 @@ void MyPoolChunk<T>::allocate(int ibin) {
 template <class T>
 double MyPoolChunk<T>::size() const {
   double bytes = npage*chunkperpage*sizeof(int);
-  bytes += npage*sizeof(T *);
-  bytes += npage*sizeof(int);
+  bytes += (double)npage*sizeof(T *);
+  bytes += (double)npage*sizeof(int);
   for (int i=0; i < npage; ++i)
-    bytes += chunkperpage*chunksize[i]*sizeof(T);
+    bytes += (double)chunkperpage*chunksize[i]*sizeof(T);
 
   return bytes;
 }