Sane SvStream* fake pointer values for 64-bit platforms

cf. <https://gerrit.libreoffice.org/#/c/13659/3> "Signed/Unsigned mismatch on
x86_64 platform on windows"

Change-Id: Ie526ee431f59be374d61fe8c38bdf2a579a7234b

include/svtools/grfmgr.hxx

@@ -33,9 +33,9 @@
 // AutoSwap defines
 
 #define GRFMGR_AUTOSWAPSTREAM_LINK      (reinterpret_cast<SvStream*>(0x00000000UL))
-#define GRFMGR_AUTOSWAPSTREAM_LOADED    (reinterpret_cast<SvStream*>(0xfffffffdUL))
-#define GRFMGR_AUTOSWAPSTREAM_TEMP      (reinterpret_cast<SvStream*>(0xfffffffeUL))
-#define GRFMGR_AUTOSWAPSTREAM_NONE      (reinterpret_cast<SvStream*>(0xffffffffUL))
+#define GRFMGR_AUTOSWAPSTREAM_LOADED reinterpret_cast<SvStream*>(sal_IntPtr(-3))
+#define GRFMGR_AUTOSWAPSTREAM_TEMP   reinterpret_cast<SvStream*>(sal_IntPtr(-2))
+#define GRFMGR_AUTOSWAPSTREAM_NONE   reinterpret_cast<SvStream*>(sal_IntPtr(-1))
 
 // Adjustment defines