contrib: update opendht to 1.7.5rc3

Change-Id: I59dfda28dcf94faebaae1cbeb89f0a7a9229c2ad

contrib/src/opendht/SHA512SUMS

-492cf4f0ac4352551952754a68c5bd584c5f2b0b4d1b4faebf170a508d7e83115235cbc0458cbe367f3726484da19194990b738338c2ff8c87657bc78fb74f19  opendht-1.7.5rc2.tar.gz
+1e0962ef28e166d085806af318b2d18ec8793830e5aef6196680f771cc46ac07cb4858872783c0c5e69b47ee0bd705c028b79b4b6b955582a9f7ded8f6cd5ba1  opendht-1.7.5rc3.tar.gz

contrib/src/opendht/rules.mak

 # OPENDHT
-OPENDHT_VERSION := 1.7.5rc2
+OPENDHT_VERSION := 1.7.5rc3
 OPENDHT_URL := https://github.com/savoirfairelinux/opendht/archive/$(OPENDHT_VERSION).tar.gz
 
 PKGS += opendht