docs: add notes about deprecated options and function names

Also remove two notes that are obsolete by now.

doc/nano.texi

@@ -909,6 +909,7 @@ Use this color combination for the title bar.
 @item set trimblanks
 Remove trailing whitespace from wrapped lines when automatic
 hard-wrapping occurs or when text is justified.
+(The old form of this option, @code{set justifytrim}, is deprecated.)
 
 @item set unix
 Save a file by default in Unix format.  This overrides nano's
@@ -1349,6 +1350,7 @@ Toggles the presence of the two-line list of key bindings at the bottom of the s
 
 @item constantshow
 Toggles the constant display of the current line, column, and character positions.
+(The form @code{constupdate} is deprecated.)
 
 @item morespace
 Toggles the presence of the blank line that 'separates' the title bar from the file text.
@@ -1377,6 +1379,7 @@ Toggles whether new lines will contain the same amount of whitespace as the prec
 @item cutfromcursor
 Toggles whether cutting text will cut the whole line or just from the current cursor
 position to the end of the line.
+(The form @code{cuttoend} is deprecated.)
 
 @item nowrap
 Toggles whether long lines will be hard-wrapped to the next line.

doc/nanorc.5

@@ -273,6 +273,7 @@ And either "\fIfgcolor\fR" or ",\fIbgcolor\fR" may be left out.
 .B set trimblanks
 Remove trailing whitespace from wrapped lines when automatic
 hard-wrapping occurs or when text is justified.
+(The old form of this option, '\fBset justifytrim\fR', is deprecated.)
 .TP
 .B set unix
 Save a file by default in Unix format.  This overrides nano's
@@ -705,6 +706,7 @@ Toggles the presence of the two-line list of key bindings at the bottom of the s
 .TP
 .B constantshow
 Toggles the constant display of the current line, column, and character positions.
+(The form 'constupdate' is deprecated.)
 .TP
 .B morespace
 Toggles the presence of the blank line that 'separates' the title bar from the file text.
@@ -733,6 +735,7 @@ Toggles whether new lines will contain the same amount of whitespace as the prec
 .B cutfromcursor
 Toggles whether cutting text will cut the whole line or just from the current cursor
 position to the end of the line.
+(The form 'cuttoend' is deprecated.)
 .TP
 .B nowrap
 Toggles whether long lines will be hard-wrapped to the next line.

doc/sample.nanorc.in

@@ -43,7 +43,6 @@
 ## Constantly display the cursor position in the status bar.  Note that
 ## this overrides "quickblank".
 # set constantshow
-## (The old form, 'const', is deprecated.)
 
 ## Use cut-from-cursor-to-end-of-line by default.
 # set cutfromcursor
@@ -107,7 +106,6 @@
 
 ## Remember the cursor position in each file for the next editing session.
 # set positionlog
-## (The old form, 'poslog', is deprecated.)
 
 ## Preserve the XON and XOFF keys (^Q and ^S).
 # set preserve
@@ -174,6 +172,7 @@
 
 ## Snip whitespace at the end of lines when justifying or hard-wrapping.
 # set trimblanks
+## (The old form, 'justifytrim', is deprecated.)
 
 ## Disallow file modification.  Why would you want this in an rcfile? ;)
 # set view