References: 
1. https://bugzilla.redhat.com/show_bug.cgi?id=543906

2. https://bugzilla.redhat.com/show_bug.cgi?id=497090



3. http://bugs.icu-project.org/trac/ticket/7601

4. https://bugs.freedesktop.org/show_bug.cgi?id=27485



Decomposition is sometimes required for contextual alternates. Pango as well as
uniscribe, seem to have this feature for indic (CTL scripts).