The mentioned point is documented in the Wiki now

wenns · wenns · commit 7dce80cc8445 · 2013-07-28T22:54:45.000+02:00
diff --git a/DocumentationBacklog.txt b/DocumentationBacklog.txt
@@ -1,5 +0,0 @@
-- Fix the documentation of 
-      sonar.cxx.suffixes.sources and sonar.cxx.suffixes.headers:
-  the extensions should be given inclusive dot now.
-
-
