runtime(vim): Update base syntax, match :wincmd

Match the full :wincmd command syntax.

Allow for oneline assignment to Vim9 variables named winc[md].

Fixes #18368.

Signed-off-by: Doug Kearns <dougkearns@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>

runtime/syntax/testdir/input/vim_ex_wincmd.vim

@@ -0,0 +1,67 @@
+" Vim :wincmd command
+" VIM_TEST_SETUP hi link vimWincmdArg Todo
+" VIM_TEST_SETUP hi link vimCmdSep Special
+
+
+wincmd s
+wincmd S
+wincmd v
+wincmd n
+wincmd ^
+wincmd :
+wincmd q
+wincmd o
+wincmd j
+wincmd k
+wincmd h
+wincmd l
+wincmd w
+wincmd W
+wincmd t
+wincmd b
+wincmd p
+wincmd P
+wincmd r
+wincmd R
+wincmd x
+wincmd K
+wincmd J
+wincmd H
+wincmd L
+wincmd T
+wincmd =
+wincmd -
+wincmd +
+wincmd _
+wincmd <
+wincmd >
+wincmd |
+wincmd ]
+wincmd g ]
+wincmd f
+wincmd F
+wincmd gf
+wincmd gF
+wincmd gt
+wincmd gT
+wincmd z
+wincmd }
+wincmd g }
+
+
+wincmd | | echo "Foo"
+wincmd | " comment
+wincmd s | echo "Foo"
+wincmd s " comment
+
+
+def Vim9Context()
+  var wincmd = 42
+  wincmd = 42
+  :wincmd =
+  wincmd = # comment
+  wincmd = | echo "Foo"
+  # KNOWN: incorrectly matches as the Ex command rather than a variable
+  wincmd =
+enddef
+