Fix Ada bindings on x64.

Author: spectralio

contrib/ada/zlib-thin.adb

@@ -12,7 +12,8 @@ package body ZLib.Thin is
 
    ZLIB_VERSION  : constant Chars_Ptr := zlibVersion;
 
-   Z_Stream_Size : constant Int := Z_Stream'Size / System.Storage_Unit;
+   Dummy : Z_Stream;
+   Z_Stream_Size : constant Int := Dummy'Size / System.Storage_Unit;
 
    --------------
    -- Avail_In --