runtime(vim): Update base-syntax, improve :menu{,translate} highlighting (#14162)

Improve :menu and :menutranslate highlighting.

- Match args to :menutranslation and :popup.
- Only highlight special notation in {rhs} of :menu, like :map.
- Allow line continuations in {rhs} of :menu and between {english} and
  {mylang} of :menutranslation, matching common usage.
- Bug fixes.

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

runtime/syntax/testdir/input/vim_ex_menu.vim

@@ -0,0 +1,73 @@
+" Vim :menu commands
+
+" :help disable menus
+menu disable &File.&Open\.\.\.
+amenu enable *
+amenu disable &Tools.*
+
+
+" :help menu-examples
+nmenu Words.Add\ Var         wb"zye:menu! Words.<C-R>z <C-R>z<CR>
+nmenu Words.Remove\ Var      wb"zye:unmenu! Words.<C-R>z<CR>
+vmenu Words.Add\ Var         "zy:menu! Words.<C-R>z <C-R>z <CR>
+vmenu Words.Remove\ Var      "zy:unmenu! Words.<C-R>z<CR>
+imenu Words.Add\ Var         <Esc>wb"zye:menu! Words.<C-R>z <C-R>z<CR>a
+imenu Words.Remove\ Var      <Esc>wb"zye:unmenu! Words.<C-R>z<CR>a
+
+
+" special keys
+menu <silent> &Foo\ bar  :echo "Foobar"<CR>
+menu <special> &Foo\ bar :echo "Foobar"<CR>
+menu <script> &Foo\ bar  :echo "Foobar"<CR>
+menu <silent> <special> &Foo\ bar :echo "Foobar"<CR>
+menu <silent> <special> <script> &Foo\ bar :echo "Foobar"<CR>
+
+
+function Foo()
+  menu <silent> &Foo\ bar :echo "Foobar"<CR>
+endfunction
+
+
+" Example: runtime/menu.vim (modified)
+an <silent> 10.330 &File.&Close<Tab>:close :confirm close<CR>
+
+an <silent> 10.330 &File.&Close<Tab>:close
+        \ :if winheight(2) < 0 && tabpagewinnr(2) == 0 <Bar>
+	\   confirm enew <Bar>
+	\ else <Bar>
+	\   confirm close <Bar>
+	\ endif<CR>
+
+an <silent> 10.330 &File.&Close<Tab>:close
+	"\ comment
+        \ :if winheight(2) < 0 && tabpagewinnr(2) == 0 <Bar>
+	"\ comment
+	\   confirm enew <Bar>
+	"\ comment
+	\ else <Bar>
+	"\ comment
+	\   confirm close <Bar>
+	"\ comment
+	\ endif<CR>
+
+an <silent> 10.330 &File.&Close<Tab>:close :if winheight(2) < 0 && tabpagewinnr(2) == 0 <Bar>
+	\   confirm enew <Bar>
+	\ else <Bar>
+	\   confirm close <Bar>
+	\ endif<CR>
+
+an <silent> 10.330 &File.&Close<Tab>:close :if winheight(2) < 0 && tabpagewinnr(2) == 0 <Bar>
+	"\ comment
+	\   confirm enew <Bar>
+	"\ comment
+	\ else <Bar>
+	"\ comment
+	\   confirm close <Bar>
+	"\ comment
+	\ endif<CR>
+
+
+" popup menus
+popup &Foo  | echo "Foo"
+popup! &Foo | echo "Foo"
+

runtime/syntax/testdir/input/vim_ex_menutranslate.vim

@@ -0,0 +1,51 @@
+" Vim :menutranslate command
+
+menutranslate clear
+menutranslate clear | echo "Foo"
+menutranslate clear " comment
+
+menutranslate &Foo\ bar &FuBar | echo "Foo"
+
+menutranslate &Foo\ bar &FuBar " comment
+menutranslate \"&Foo"\ bar \"&FuBar
+menutranslate &Foo\ "bar" &FuBar
+
+menutranslate &Foo\ bar
+      \ &Fubar | echo "Foo"
+
+menutranslate
+      \ &Foo\ bar
+      \ &Fubar | echo "Foo"
+
+menutranslate
+      \ &Foo\ bar
+      \ &Fubar| echo "Foo"
+
+menutranslate
+      \ &Foo\ bar
+      \ &Fubar
+      \ | echo "Foo"
+
+menutranslate &Foo\ bar
+      "\ comment
+      \ &Fubar | echo "Foo"
+
+menutranslate
+      "\ comment
+      \ &Foo\ bar
+      "\ comment
+      \ &Fubar | echo "Foo"
+
+menutranslate
+      \ &Foo\ bar
+      "\ comment
+      \ &Fubar| echo "Foo"
+      "\ comment
+
+menutranslate
+      "\ comment
+      \ &Foo\ bar
+      "\ comment
+      \ &Fubar
+      \ | echo "Foo"
+