Fix uses of @kindex in the Emacs manual

* doc/emacs/programs.texi (Expressions, Semantic, Hungry Delete):
* doc/emacs/mark.texi (Global Mark Ring)
(Disabled Transient Mark):
* doc/emacs/buffers.texi (Select Buffer):
* doc/emacs/mule.texi (File Name Coding): Fix @kindex entries
which used @key.  Reported by Marcin Borkowski <mbork@mbork.pl>.

doc/emacs/buffers.texi

@@ -110,8 +110,8 @@ it, Emacs asks for the file name to use, and the buffer's major mode
 is re-established taking that file name into account (@pxref{Choosing
 Modes}).
 
-@kindex C-x @key{LEFT}
-@kindex C-x @key{RIGHT}
+@kindex C-x LEFT
+@kindex C-x RIGHT
 @findex next-buffer
 @findex previous-buffer
   For conveniently switching between a few buffers, use the commands

doc/emacs/mark.texi

@@ -367,7 +367,7 @@ of buffers that you have been in, and, for each buffer, a place where
 you set the mark.  The length of the global mark ring is controlled by
 @code{global-mark-ring-max}, and is 16 by default.
 
-@kindex C-x C-@key{SPC}
+@kindex C-x C-SPC
 @findex pop-global-mark
   The command @kbd{C-x C-@key{SPC}} (@code{pop-global-mark}) jumps to
 the buffer and position of the latest entry in the global ring.  It also
@@ -449,7 +449,7 @@ using @kbd{C-@key{SPC} C-@key{SPC}} or @kbd{C-u C-x C-x}.
 
 @table @kbd
 @item C-@key{SPC} C-@key{SPC}
-@kindex C-@key{SPC} C-@key{SPC}
+@kindex C-SPC C-SPC
 Set the mark at point (like plain @kbd{C-@key{SPC}}) and enable
 Transient Mark mode just once, until the mark is deactivated.  (This
 is not really a separate command; you are using the @kbd{C-@key{SPC}}

doc/emacs/mule.texi

@@ -1198,7 +1198,7 @@ names (@code{set-file-name-coding-system}).
 @end table
 
 @findex set-file-name-coding-system
-@kindex C-x @key{RET} F
+@kindex C-x RET F
 @cindex file names with non-@acronym{ASCII} characters
   The command @kbd{C-x @key{RET} F} (@code{set-file-name-coding-system})
 specifies a coding system to use for encoding file @emph{names}.  It

doc/emacs/programs.texi

@@ -712,7 +712,7 @@ before it.  An argument of zero, rather than doing nothing, transposes
 the balanced expressions ending at or after point and the mark.
 
 @kindex C-M-@@
-@kindex C-M-@key{SPC}
+@kindex C-M-SPC
 @findex mark-sexp
   To operate on balanced expressions with a command which acts on the
 region, type @kbd{C-M-@key{SPC}} (@code{mark-sexp}).  This sets the
@@ -1467,7 +1467,7 @@ Prompt for the name of a function defined in any file Emacs has
 parsed, and move point there (@code{semantic-complete-jump}).
 
 @item C-c , @key{SPC}
-@kindex C-c , @key{SPC}
+@kindex C-c , SPC
 Display a list of possible completions for the symbol at point
 (@code{semantic-complete-analyze-inline}).  This also activates a set
 of special key bindings for choosing a completion: @key{RET} accepts
@@ -1716,8 +1716,8 @@ preprocessor commands.
 @item C-c C-@key{DEL}
 @itemx C-c @key{DEL}
 @findex c-hungry-delete-backwards
-@kindex C-c C-@key{DEL} (C Mode)
-@kindex C-c @key{DEL} (C Mode)
+@kindex C-c C-DEL (C Mode)
+@kindex C-c DEL (C Mode)
 Delete the entire block of whitespace preceding point (@code{c-hungry-delete-backwards}).
 
 @item C-c C-d
@@ -1725,8 +1725,8 @@ Delete the entire block of whitespace preceding point (@code{c-hungry-delete-bac
 @itemx C-c @key{Delete}
 @findex c-hungry-delete-forward
 @kindex C-c C-d (C Mode)
-@kindex C-c C-@key{Delete} (C Mode)
-@kindex C-c @key{Delete} (C Mode)
+@kindex C-c C-Delete (C Mode)
+@kindex C-c Delete (C Mode)
 Delete the entire block of whitespace after point (@code{c-hungry-delete-forward}).
 @end table