rdoff/rdfwriteheader: Write object length and header length in correct order

Compared to 2.12.xx rdfwriteheader() writes the object length and header
length in flipped order.  Issue seems to have been introduced by commit
8dc9653.

BR3392717

Signed-off-by: Ozkan Sezer <sezeroz@gmail.com>
Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>

Author: sezero

rdoff/rdoff.c

@@ -612,8 +612,8 @@ int rdfwriteheader(FILE * fp, rdf_headerbuf * h)
 
     l = membuflength(h->buf);
     l2 = l + 14 + 10 * h->nsegments + h->seglength;
-    fwriteint32_t(l, fp);
-    fwriteint32_t(l2, fp);
+    fwriteint32_t(l2, fp);      /* object length */
+    fwriteint32_t(l, fp);       /* header length */
 
     membufdump(h->buf, fp);