[trac686] set library version for libdns++

Since last release
isc::dns::rdata::generic::NSEC::getNextName()
was introduced.
So increment current and age.

src/lib/dns/Makefile.am

@@ -84,6 +84,8 @@ BUILT_SOURCES += rdataclass.h rdataclass.cc
 
 lib_LTLIBRARIES = libdns++.la
 
+libdns___la_LDFLAGS = -no-undefined -version-info 1:0:1
+
 libdns___la_SOURCES =
 libdns___la_SOURCES += edns.h edns.cc
 libdns___la_SOURCES += exceptions.h exceptions.cc