Checkdoc fixes in emulation/*.el

* lisp/emulation/cua-base.el:
* lisp/emulation/viper-mous.el (viper-parse-mouse-key):
* lisp/emulation/viper.el (viper-major-mode-modifier-list):
Checkdoc fixes.

lisp/emulation/cua-base.el

@@ -154,7 +154,7 @@
 ;;
 ;; To start a rectangle, use [C-return] and extend it using the normal
 ;; movement keys (up, down, left, right, home, end, C-home,
-;; C-end). Once the rectangle has the desired size, you can cut or
+;; C-end).  Once the rectangle has the desired size, you can cut or
 ;; copy it using C-x and C-c (or C-w and M-w), and you can
 ;; subsequently insert it - as a rectangle - using C-v (or C-y).  So
 ;; the only new command you need to know to work with cua-mode

lisp/emulation/viper-mous.el

@@ -456,7 +456,7 @@ bindings in the Viper manual."
 		   (if (eq 'up event-type)
 		       "mouse-3" "down-mouse-3"))
 		  (t (error
-		      "%S: invalid button number, %S" key-var key)))
+                      "%S: Invalid button number, %S" key-var key)))
 	    meta-spec
 	    (if (memq 'meta key) "M-" "")
 	    shift-spec

lisp/emulation/viper.el

@@ -486,7 +486,7 @@ unless it is coming up in a wrong Viper state."
   "List specifying how to modify the various major modes to enable some Viperisms.
 The list has the structure: ((mode viper-state keymap) (mode viper-state
 keymap) ...).  If `mode' is on the list, the `keymap' will be made active (on
-the minor-mode-map-alist) in the specified viper state.
+the `minor-mode-map-alist') in the specified viper state.
 If you change this list, have to restart Emacs for the change to take effect.
 However, if you did the change through the customization widget, then Emacs
 needs to be restarted only if you deleted a triple mode-state-keymap from the