fix external storage showing as overfull (#2529)

src/main/java/com/refinedmods/refinedstorage/api/storage/externalstorage/IExternalStorage.java

@@ -24,5 +24,5 @@ public interface IExternalStorage<T> extends IStorage<T> {
     /**
      * @return the capacity of the connected storage
      */
-    int getCapacity();
+    long getCapacity();
 }

src/main/java/com/refinedmods/refinedstorage/apiimpl/storage/externalstorage/FluidExternalStorage.java

@@ -43,11 +43,11 @@ public class FluidExternalStorage implements IExternalStorage<FluidStack> {
     }
 
     @Override
-    public int getCapacity() {
+    public long getCapacity() {
         IFluidHandler fluidHandler = handlerSupplier.get();
 
         if (fluidHandler != null) {
-            int cap = 0;
+            long cap = 0;
 
             for (int i = 0; i < fluidHandler.getTanks(); ++i) {
                 cap += fluidHandler.getTankCapacity(i);

src/main/java/com/refinedmods/refinedstorage/apiimpl/storage/externalstorage/ItemExternalStorage.java

@@ -44,17 +44,17 @@ public class ItemExternalStorage implements IExternalStorage<ItemStack> {
     }
 
     @Override
-    public int getCapacity() {
+    public long getCapacity() {
         IItemHandler handler = handlerSupplier.get();
 
         if (handler == null) {
             return 0;
         }
 
-        int capacity = 0;
+        long capacity = 0;
 
         for (int i = 0; i < handler.getSlots(); ++i) {
-            capacity += Math.min(handler.getSlotLimit(i), handler.getStackInSlot(i).getMaxStackSize());
+            capacity += handler.getSlotLimit(i);
         }
 
         return capacity;