Simplify format specifiers

It turns out that we can use %zu and %llu on Win32, provided we
include PosixSource everywhere we want to use them.

includes/Rts.h

@@ -143,26 +143,10 @@ void _assertFail(const char *filename, unsigned int linenum)
 #define USED_IF_NOT_THREADS
 #endif
 
-#if SIZEOF_VOID_P == 8
-# define FMT_SizeT    "zu"
-# define FMT_HexSizeT "zx"
-# define FMT_Word     "zu"
-# define FMT_Int      "zd"
-#elif SIZEOF_VOID_P == 4
-# if defined(mingw32_HOST_OS)
-#  define FMT_SizeT    "u"
-#  define FMT_HexSizeT "x"
-#  define FMT_Word     "u"
-#  define FMT_Int      "d"
-# else
-#  define FMT_SizeT    "zu"
-#  define FMT_HexSizeT "zx"
-#  define FMT_Word     "zu"
-#  define FMT_Int      "zd"
-# endif
-#else
-# error Cannot handle this word size
-#endif
+#define FMT_SizeT    "zu"
+#define FMT_HexSizeT "zx"
+#define FMT_Word     "zu"
+#define FMT_Int      "zd"
 
 /*
  * Getting printf formats right for platform-dependent typedefs
@@ -171,16 +155,9 @@ void _assertFail(const char *filename, unsigned int linenum)
 #define FMT_Word64 "lu"
 #define FMT_Int64  "ld"
 #else
-#if defined(mingw32_HOST_OS) && defined(i386_HOST_ARCH)
-/* mingw doesn't understand %llu/%lld - it treats them as 32-bit
-   rather than 64-bit */
-#define FMT_Word64 "I64u"
-#define FMT_Int64  "I64d"
-#else
 #define FMT_Word64 "llu"
 #define FMT_Int64  "lld"
 #endif
-#endif
 
 /* -----------------------------------------------------------------------------
    Time values in the RTS