use %p to printf pointers since %x doesn't work properly on tru64 for this

(and besides, we should be using the same %-code for all pointers)

lib/memdebug.c

@@ -201,7 +201,7 @@ void *curl_dorealloc(void *ptr, size_t wantedsize,
 
   mem=(struct memdebug *)(Curl_crealloc)(mem, size);
   if(logfile)
-    fprintf(logfile, "MEM %s:%d realloc(0x%x, %zd) = %p\n",
+    fprintf(logfile, "MEM %s:%d realloc(%p, %zd) = %p\n",
             source, line, ptr, wantedsize, mem?mem->mem:NULL);
 
   if(mem) {