(s - NULL & 1) would not compiler under GCC 4.0.0. Changed to char*
subtraction so that it will compile under MS VC++ and GCC.
diff --git a/expat/lib/xmlparse.c b/expat/lib/xmlparse.c
index 184d8f6..449bd92 100644
--- a/expat/lib/xmlparse.c
+++ b/expat/lib/xmlparse.c
@@ -28,7 +28,8 @@
#define XmlGetInternalEncoding XmlGetUtf16InternalEncoding
#define XmlGetInternalEncodingNS XmlGetUtf16InternalEncodingNS
#define XmlEncode XmlUtf16Encode
-#define MUST_CONVERT(enc, s) (!(enc)->isUtf16 || ((s - NULL) & 1))
+/* Using pointer subtraction to convert to integer type. */
+#define MUST_CONVERT(enc, s) (!(enc)->isUtf16 || (((char *)(s) - (char *)NULL) & 1))
typedef unsigned short ICHAR;
#else
#define XML_ENCODE_MAX XML_UTF8_ENCODE_MAX
