tool_getparam.c: Fixed compilation warnings

There is an implicit conversion from "unsigned long" to "long"

lib/warnless.c

@@ -174,6 +174,25 @@ int curlx_ultosi(unsigned long ulnum)
 #endif
 }
 
+/*
+** unsigned size_t to signed curl_off_t
+*/
+
+curl_off_t curlx_uztoso(size_t uznum)
+{
+#ifdef __INTEL_COMPILER
+#  pragma warning(push)
+#  pragma warning(disable:810) /* conversion may lose significant bits */
+#endif
+
+  DEBUGASSERT(uznum <= (size_t) CURL_MASK_SCOFFT);
+  return (curl_off_t)(uznum & (size_t) CURL_MASK_SCOFFT);
+
+#ifdef __INTEL_COMPILER
+#  pragma warning(pop)
+#endif
+}
+
 /*
 ** unsigned size_t to signed int
 */