patch 9.1.1284: not possible to configure pum truncation char

Problem:  not possible to configure the completion menu truncation
          character
Solution: add the "trunc" suboption to the 'fillchars' setting to
          configure the truncation indicator (glepnir).

closes: #17006

Co-authored-by: zeertzjq <zeertzjq@outlook.com>
Signed-off-by: glepnir <glephunter@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/runtime/doc/options.txt b/runtime/doc/options.txt
index 7720769..f90a335 100644
--- a/runtime/doc/options.txt
+++ b/runtime/doc/options.txt
@@ -1,4 +1,4 @@
-*options.txt*	For Vim version 9.1.  Last change: 2025 Apr 06
+*options.txt*	For Vim version 9.1.  Last change: 2025 Apr 07
 
 
 		  VIM REFERENCE MANUAL	  by Bram Moolenaar
@@ -3603,8 +3603,8 @@
 						*'fillchars'* *'fcs'*
 'fillchars' 'fcs'	string	(default "vert:|,fold:-,eob:~,lastline:@")
 			global or local to window |global-local|
-	Characters to fill the statuslines, vertical separators and special
-	lines in the window.
+	Characters to fill the statuslines, vertical separators, special
+	lines in the window and truncated text in the |ins-completion-menu|.
 	It is a comma-separated list of items.  Each item has a name, a colon
 	and the value of that item: |E1511|
 
@@ -3619,6 +3619,8 @@
 	  diff		'-'		deleted lines of the 'diff' option
 	  eob		'~'		empty lines below the end of a buffer
 	  lastline	'@'		'display' contains lastline/truncate
+	  trunc		'>'		truncated text in the
+					|ins-completion-menu|.
 
 	Any one that is omitted will fall back to the default.
 
@@ -3635,9 +3637,14 @@
 	  stlnc		StatusLineNC		|hl-StatusLineNC|
 	  vert		VertSplit		|hl-VertSplit|
 	  fold		Folded			|hl-Folded|
+	  foldopen	FoldColumn		|hl-FoldColumn|
+	  foldclose	FoldColumn		|hl-FoldColumn|
+	  foldsep	FoldColumn		|hl-FoldColumn|
 	  diff		DiffDelete		|hl-DiffDelete|
 	  eob		EndOfBuffer		|hl-EndOfBuffer|
 	  lastline	NonText			|hl-NonText|
+	  trunc		one of the many Popup menu highlighting groups like
+			|hl-PmenuSel|
 
 						*'findfunc'* *'ffu'* *E1514*
 'findfunc' 'ffu'	string	(default empty)
@@ -6513,7 +6520,9 @@
 	Determines the maximum width to use for the popup menu for completion.
 	When zero, there is no maximum width limit, otherwise the popup menu
 	will never be wider than this value.  Truncated text will be indicated
-	by "..." at the end.  Takes precedence over 'pumwidth'.
+	by "trunc" value of 'fillchars' option.
+
+	This option takes precedence over 'pumwidth'.
 	|ins-completion-menu|.
 
 						*'pumwidth'* *'pw'*