patch 8.1.0487: no menus specifically for the terminal window

Problem:    No menus specifically for the terminal window.
Solution:   Add :tlmenu. (Yee Cheng Chin, closes #3439) Add a menu test.
diff --git a/runtime/syntax/vim.vim b/runtime/syntax/vim.vim
index 30c3f2f..abd2d18 100644
--- a/runtime/syntax/vim.vim
+++ b/runtime/syntax/vim.vim
@@ -407,7 +407,7 @@
 " Menus {{{2
 " =====
 syn cluster	vimMenuList contains=vimMenuBang,vimMenuPriority,vimMenuName,vimMenuMod
-syn keyword	vimCommand	am[enu] an[oremenu] aun[menu] cme[nu] cnoreme[nu] cunme[nu] ime[nu] inoreme[nu] iunme[nu] me[nu] nme[nu] nnoreme[nu] noreme[nu] nunme[nu] ome[nu] onoreme[nu] ounme[nu] unme[nu] vme[nu] vnoreme[nu] vunme[nu] skipwhite nextgroup=@vimMenuList
+syn keyword	vimCommand	am[enu] an[oremenu] aun[menu] cme[nu] cnoreme[nu] cunme[nu] ime[nu] inoreme[nu] iunme[nu] me[nu] nme[nu] nnoreme[nu] noreme[nu] nunme[nu] ome[nu] onoreme[nu] ounme[nu] tlm[enu] tln[oremenu] tlu[nmenu] unme[nu] vme[nu] vnoreme[nu] vunme[nu] skipwhite nextgroup=@vimMenuList
 syn match	vimMenuName	"[^ \t\\<]\+"	contained nextgroup=vimMenuNameMore,vimMenuMap
 syn match	vimMenuPriority	"\d\+\(\.\d\+\)*"	contained skipwhite nextgroup=vimMenuName
 syn match	vimMenuNameMore	"\c\\\s\|<tab>\|\\\."	contained nextgroup=vimMenuName,vimMenuNameMore contains=vimNotation