2017-03-22  Murray Cumming  <murrayc@murrayc.com>

	2.51.6

	This is the first 2.51.* version of glibmm-2.4.
	There were previously some 2.51 versions of glibmm-2.52, which
	installed in parallel with glibmm-2.4,
	but there will not be any stable version of glibmm-2.52.
	There might instead be a stable version of glibmm-2.54 eventually.