Parameterize the sourceforge mirror to ease switching in case one of the mirrors is down.

Makefile

@@ -10,14 +10,15 @@ SNMP_VERSION      = 5.7.3
 OPENSSL_VERSION   = 1.0.1p
 CPPDRV_VERSION    = 2.0.1
 LIBUV_VERSION     = 0.10.36
+SOURCEFORGE_MROR  = netcologne
 
 BOOST_VERSION_U   = $(subst .,_,$(BOOST_VERSION))
 DISTFILES =	apache-cassandra-$(CASSANDRA_VERSION).tar.gz;http://mirrors.sonic.net/apache/cassandra/$(CASSANDRA_VERSION)/apache-cassandra-$(CASSANDRA_VERSION)-bin.tar.gz \
 		mosquitto-$(MOSQUITTO_VERSION).tar.gz;http://mosquitto.org/files/source/mosquitto-$(MOSQUITTO_VERSION).tar.gz \
 		rudeconfig-5.0.5.tar.gz;http://rudeserver.com/config/download/rudeconfig-5.0.5.tar.gz \
-		OpenIPMI-2.0.21.tar.gz;http://cznic.dl.sourceforge.net/project/openipmi/OpenIPMI%202.0%20Library/OpenIPMI-2.0.21.tar.gz \
-		boost_$(BOOST_VERSION_U).tar.gz;http://cznic.dl.sourceforge.net/project/boost/boost/$(BOOST_VERSION)/boost_$(BOOST_VERSION_U).tar.gz \
-		net-snmp-$(SNMP_VERSION).zip;http://cznic.dl.sourceforge.net/project/net-snmp/net-snmp/$(SNMP_VERSION)/net-snmp-$(SNMP_VERSION).zip \
+		OpenIPMI-2.0.21.tar.gz;http://$(SOURCEFORGE_MROR).dl.sourceforge.net/project/openipmi/OpenIPMI%202.0%20Library/OpenIPMI-2.0.21.tar.gz \
+		boost_$(BOOST_VERSION_U).tar.gz;http://$(SOURCEFORGE_MROR).dl.sourceforge.net/project/boost/boost/$(BOOST_VERSION)/boost_$(BOOST_VERSION_U).tar.gz \
+		net-snmp-$(SNMP_VERSION).zip;http://$(SOURCEFORGE_MROR).dl.sourceforge.net/project/net-snmp/net-snmp/$(SNMP_VERSION)/net-snmp-$(SNMP_VERSION).zip \
 		openssl-$(OPENSSL_VERSION).tar.gz;ftp://ftp.pca.dfn.de/pub/tools/net/openssl/source/openssl-$(OPENSSL_VERSION).tar.gz \
 		cpp-driver-$(CPPDRV_VERSION).tar.gz;https://github.com/datastax/cpp-driver/archive/$(CPPDRV_VERSION).tar.gz \
 		libuv-v$(LIBUV_VERSION).tar.gz;http://dist.libuv.org/dist/v$(LIBUV_VERSION)/libuv-v$(LIBUV_VERSION).tar.gz