correctly define {U,}INTPTR_T on 64bit Windows

Fixes crashes on Windows when loading jxr compressed czi files.
This library, despite being originally a Windows product, didn't
support 64bit Windows at all. There's a special code path for 32bit
Windows with handwritten assembler code, which may have worked back
then. But the 64bit code path in the generic "ANSI" platform only
checked `__LP64__`, which isn't defined by MSVC. Fix this by using
`stdint.h`'s `{u},intptr_t` here to get portable code.

image/sys/ansi.h

@@ -27,6 +27,8 @@
 //*@@@---@@@@******************************************************************
 #pragma once
 
+#include <stdint.h>
+
 //================================
 // bitio functions
 //================================
@@ -42,11 +44,5 @@
 //================================
 // common defines
 //================================
-#if __LP64__
-#define UINTPTR_T unsigned long long
-#define INTPTR_T long long
-#else
-#define UINTPTR_T unsigned int
-#define INTPTR_T int
-#endif
-
+#define UINTPTR_T uintptr_t
+#define INTPTR_T intptr_t