filetime should be -1 if the remote time was unknown as 0 is actually a

valid time. we now store the filetime as a long to know for sure it can
hold -1 (there exist some unsigned time_t cases)

lib/getinfo.c

@@ -46,7 +46,7 @@ CURLcode Curl_initinfo(struct SessionHandle *data)
 
   info->httpcode = 0;
   info->httpversion=0;
-  info->filetime=0;
+  info->filetime=-1; /* -1 is an illegal time and thus means unknown */
 
   return CURLE_OK;
 }

lib/transfer.c

@@ -627,7 +627,7 @@ Transfer(struct connectdata *c_conn)
                       (data->set.timecondition || data->set.get_filetime) ) {
                 time_t secs=time(NULL);
                 timeofdoc = curl_getdate(p+strlen("Last-Modified:"), &secs);
-                if(data->set.get_filetime)
+                if(data->set.get_filetime>=0)
                   data->info.filetime = timeofdoc;
               }
               else if ((httpcode >= 300 && httpcode < 400) &&

lib/urldata.h

@@ -352,7 +352,7 @@ struct connectdata {
 struct PureInfo {
   int httpcode;
   int httpversion;
-  time_t filetime; /* If requested, this is might get set. It may be 0 if
+  long filetime; /* If requested, this is might get set. Set to -1 if
                     the time was unretrievable */
   long header_size;  /* size of read header(s) in bytes */
   long request_size; /* the amount of bytes sent in the request(s) */