maint: post-release administrivia

* NEWS: Add header line for the next release.
diff --git a/NEWS b/NEWS
index 9623754..fe40ca4 100644
--- a/NEWS
+++ b/NEWS
@@ -1,3 +1,6 @@
+Noteworthy changes in release ?.?? (????-??-??)
+===============================================
+
 Noteworthy changes in release 4.11 (2015-12-21)
 ===============================================