Peercoin: Set v0.5 release (v0.5.2) upgrade deadline to April 25, 2016. For nodes running v0.5.0 RC1 and v0.5.1 RC2 release candidates, upgrade deadline is March 14, 2016
Peercoin: Set v0.5 release (v0.5.2) upgrade deadline to April 25, 2016.
For nodes running v0.5.0 RC1 and v0.5.1 RC2 release candidates,
upgrade deadline is March 14, 2016

(cherry picked from commit 381a5e0dd4aa076fc3f414e13e08818809256b2c)

Conflicts:
	src/version.h

peercoin/peercoin,peercoin/peercoin,peercoin/peercoin,peercoin/peercoin,peercoin/peercoin,DigitalPandacoin/pandacoin,glv2/peerunity,peercoin/peercoin,ppcoin/ppcoin,DigitalPandacoin/pandacoin,DigitalPandacoin/pandacoin,DigitalPandacoin/pandacoin,ppcoin/ppcoin,DigitalPandacoin/pandacoin,glv2/peerunity,glv2/peerunity,ppcoin/ppcoin,glv2/peerunity,ppcoin/ppcoin,DigitalPandacoin/pandacoin