contrib: bump opendht -> 0.6.2

* Permanent 'put' feature;
* Enhanced search's nodes handler algorithm;
* fix bug when IPv[46] empty table, would not call some callbacks;
* man page for dhtnode;
* support for make DESTDIR= syntax;

Change-Id: I0ae58edb706a6344a45fc7c254c7cd29ef8bc90a
Reviewed-by: Edric Milaret <edric.ladent-milaret@savoirfairelinux.com>

contrib/src/opendht/rules.mak

 # OPENDHT
-OPENDHT_VERSION := 0.6.1
+OPENDHT_VERSION := 0.6.2
 OPENDHT_URL := https://github.com/savoirfairelinux/opendht/archive/$(OPENDHT_VERSION).tar.gz
 
 PKGS += opendht