Reverted the 'filetime' struct field back to a 'long' as time_t is sometimes

unsigned and we want this to be able to hold -1 for illegal/unset values.

lib/urldata.h

@@ -548,8 +548,10 @@ struct connectdata {
 struct PureInfo {
   int httpcode;
   int httpversion;
-  time_t filetime; /* If requested, this is might get set. Set to -1 if
-                      the time was unretrievable */
+  long filetime; /* If requested, this is might get set. Set to -1 if the time
+                    was unretrievable. We cannot have this of type time_t,
+                    since time_t is unsigned on several platforms such as
+                    OpenVMS. */
   long header_size;  /* size of read header(s) in bytes */
   long request_size; /* the amount of bytes sent in the request(s) */