patch 9.1.0572: cannot specify tab page closing behaviour

Problem:  cannot specify tab page closing behaviour
          (Gianluca Pacchiella)
Solution: Add the 'tabclose' option (LemonBoy).

fixes: #5967
closes: #15204

Signed-off-by: LemonBoy <thatlemon@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/runtime/doc/quickref.txt b/runtime/doc/quickref.txt
index 517fa30..42b5228 100644
--- a/runtime/doc/quickref.txt
+++ b/runtime/doc/quickref.txt
@@ -935,6 +935,7 @@
 'switchbuf'	  'swb'     sets behavior when switching to another buffer
 'synmaxcol'	  'smc'     maximum column to find syntax items
 'syntax'	  'syn'     syntax to be loaded for current buffer
+'tabclose'	  'tcl'     which tab page to focus when closing a tab
 'tabline'	  'tal'     custom format for the console tab pages line
 'tabpagemax'	  'tpm'     maximum number of tab pages for |-p| and "tab all"
 'tabstop'	  'ts'	    number of spaces that <Tab> in file uses