Related: tdf#92478 speculative win64 scanning fix

TWAIN-2.3-Spec.pdf says...

All TWAIN 2.x Sources must be prepared to work with either TWAINDSM.DLL or
TWAIN_32.DLL, which may still be used by older Applications.

The TWAIN DSM is a shared library named TWAINDSM.DLL.  There is a 32-bit and a
64-bit version of this file.

Change-Id: I047d872271573a5b2efc3ee2af4ecfc4e142a2b2
Reviewed-on: https://gerrit.libreoffice.org/26541Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>

extensions/source/scanner/scanwin.cxx

@@ -59,10 +59,12 @@ using namespace ::com::sun::star;
 #define PTWAINMSG               MSG*
 #define FIXTODOUBLE( nFix )     ((double)nFix.Whole+(double)nFix.Frac/65536.)
 #define FIXTOLONG( nFix )       ((long)floor(FIXTODOUBLE(nFix)+0.5))
-
-#if defined(_WIN32)
-#define TWAIN_LIBNAME           "TWAIN_32.DLL"
 #define TWAIN_FUNCNAME          "DSM_Entry"
+
+#if defined(TWH_64BIT)
+#    define TWAIN_LIBNAME "TWAINDSM.DLL"
+#else
+#    define TWAIN_LIBNAME "TWAIN_32.DLL"
 #endif
 
 enum TwainState