patch 8.2.3279: Vim9: cannot use block in cmdline window

Problem:    Vim9: cannot use block in cmdline window.
Solution:   Add EX_CMDWIN to the CMD_block flags. (closes #8689)

src/ex_cmds.h

@@ -1853,7 +1853,7 @@ EXCMD(CMD_at,		"@",		ex_at,
 	EX_RANGE|EX_WHOLEFOLD|EX_EXTRA|EX_TRLBAR|EX_CMDWIN|EX_LOCK_OK|EX_NONWHITE_OK,
 	ADDR_LINES),
 EXCMD(CMD_block,	"{",		ex_block,  // not found normally
-	EX_TRLBAR|EX_LOCK_OK,
+	EX_TRLBAR|EX_LOCK_OK|EX_CMDWIN,
 	ADDR_NONE),
 EXCMD(CMD_endblock,	"}",		ex_endblock,
 	EX_TRLBAR|EX_CMDWIN|EX_LOCK_OK,

src/testdir/test_vim9_cmd.vim

@@ -1338,5 +1338,18 @@ def Test_echo_void()
   CheckScriptFailure(lines, 'E1186:', 1)
 enddef
 
+def Test_cmdwin_block()
+  augroup justTesting
+    autocmd BufEnter * {
+      echomsg 'in block'
+    }
+  augroup END
+  feedkeys('q:', 'xt')
+  redraw
+  feedkeys("aclose\<CR>", 'xt')
+
+  au! justTesting
+enddef
+
 
 " vim: ts=8 sw=2 sts=2 expandtab tw=80 fdm=marker

src/version.c

@@ -755,6 +755,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    3279,
 /**/
     3278,
 /**/