closure: make Block_descriptor_1 conform to the ABI

The Blocks ABI v1 used `unsigned long int` for the `size` and `reserved`
fields.  On LLP64 targets (e.g. Windows x86_64), `uintptr_t` is larger
than `unsigned long int`.  Adjust the types to make the definition
conform to the ABI specification.

Author: compnerd

closure/Block_private.h

@@ -38,8 +38,8 @@ enum {
 
 #define BLOCK_DESCRIPTOR_1 1
 struct Block_descriptor_1 {
-    uintptr_t reserved;
-    uintptr_t size;
+    unsigned long int reserved;
+    unsigned long int size;
 };
 
 #define BLOCK_DESCRIPTOR_2 1