runtime/lua/vim/compat.lua

ref #9280
Introduce the `vim.compat` module, to help environments with system Lua
5.2+ run the build/tests. Include the module implicitly in all tests.

ref #8677
legacy `vim` module:
    beep
    buffer
    command
    dict
    eval
    firstline
    lastline
    line
    list
    open
    type
    window

runtime/lua/man.lua

@@ -1,5 +1,6 @@
+require('vim.compat')
+
 local buf_hls = {}
-local unpack = table.unpack or unpack -- luacheck: ignore
 
 local function highlight_line(line, linenr)
   local chars = {}