Address 64bit MinGW compile warning (fixes #15)

../../../xmlparse.c: In function ‘generate_hash_secret_salt’:
../../../xmlparse.c:725:42: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast]
       gather_time_entropy() ^ getpid() ^ (unsigned long)parser;
                                          ^

Thanks to Viktor Szakats.

expat/Changes

@@ -23,6 +23,7 @@ Release ??????????
             Rhodri James
             Sergei Nikulov
             Tobias Taschner
+            Viktor Szakats
 
 Release 2.2.0 Tue June 21 2016
         Security fixes:

expat/lib/xmlparse.c

@@ -719,6 +719,14 @@ gather_time_entropy(void)
 static unsigned long
 generate_hash_secret_salt(XML_Parser parser)
 {
+#if defined(__UINTPTR_TYPE__)
+# define PARSER_CAST(p)  (__UINTPTR_TYPE__)(p)
+#elif defined(_WIN64) && defined(_MSC_VER)
+# define PARSER_CAST(p)  (unsigned __int64)(p)
+#else
+# define PARSER_CAST(p)  (p)
+#endif
+
 #ifdef __CloudABI__
   unsigned long entropy;
   (void)parser;
@@ -729,7 +737,7 @@ generate_hash_secret_salt(XML_Parser parser)
   /* Process ID is 0 bits entropy if attacker has local access
    * XML_Parser address is few bits of entropy if attacker has local access */
   const unsigned long entropy =
-      gather_time_entropy() ^ getpid() ^ (unsigned long)parser;
+      gather_time_entropy() ^ getpid() ^ (unsigned long)PARSER_CAST(parser);
 
   /* Factors are 2^31-1 and 2^61-1 (Mersenne primes M31 and M61) */
   if (sizeof(unsigned long) == 4) {