Modified `rst-font-lock-extend-region` so it not crashes Emacs any
more in some situations. Thanks to Stefan Monnier for analyzing the
problem.
Change of `rst-preferred-decorations` to `rst-preferred-adornments` is
reflected by a `define-obsolete-variable-alias`. Thus older
customizations should continue to work.
Moved `rst-shift-region-left` to C-c C-r C-TAB which needs no
translation to backtab.
Minor refactorings.
git-svn-id: https://docutils.svn.sourceforge.net/svnroot/docutils/trunk@6556 929543f6-e4f2-0310-98a6-ba3bd3dd1d04