bug#32956: 26.1.50; t-m-m mark deactivation documentation

[Charles A. Roelli]

> Date: Sun, 07 Oct 2018 16:39:07 +0200
> From: charles@aurox.ch (Charles A. Roelli)
>
> But the Emacs manual does lack an index entry for "deactivating the
> mark", which seems like an area for improvement.

FWIW, this change for emacs-26 should fix it, as well as adding an
entry for activating the mark.

diff --git a/doc/emacs/mark.texi b/doc/emacs/mark.texi
index 0ffa9f7..1050587 100644
--- a/doc/emacs/mark.texi
+++ b/doc/emacs/mark.texi
@@ -17,11 +17,13 @@ Mark
 changes.
 
 @cindex active region
+@cindex activating the mark
   Setting the mark at a position in the text also @dfn{activates} it.
 When the mark is active, we say also that the region is active; Emacs
 indicates its extent by highlighting the text within it, using the
 @code{region} face (@pxref{Face Customization}).
 
+@cindex deactivating the mark
   After certain non-motion commands, including any command that
 changes the text in the buffer, Emacs automatically @dfn{deactivates}
 the mark; this turns off the highlighting.  You can also explicitly