Problem:    Detecting Lua version is not reliable.
Solution:   Add "vim.lua_version". (Ozaki Kiichi, closes #8080)

Problem:    Lua test fails.
Solution:   Fix condition. (Yegappan Lakshmanan, closes #8060)

Problem:    Lua test fails on MS-Windows.
Solution:   Fall back to old method if "lua -v" doesn't work.

Problem:    Lua test fails with Lua 5.4.3 and later.
Solution:   Check for different error messages. (Yegappan Lakshmanan,
            closes #8050)

Problem:    Lua cannot handle a passed in lambda.
Solution:   Handle VAR_PARTIAL. (Prabir Shrestha, closes #7937, closes #7936)

Problem:    Lua is initialized even when not used.
Solution:   Put lua_init() after check for "eap->skip". (Christian Brabandt,
            closes #7191).  Avoid compiler warnings.

Problem:    Lua test fails with older Lua version.
Solution:   Adjust expected error messages. (closes #6444)

Problem:    Some other tests fail.
Solution:   Adjust tests for different assert_fails() behavior.

Problem:    Insufficient test coverage for Lua.
Solution:   Add tests. (Yegappan Lakshmanan, closes #6368)  Fix uncovered
            memory leak.  Avoid unnecessary copy/free.

Problem:    Lua: cannot use table.insert() and table.remove().
Solution:   Add the list functions. (Prabir Shrestha, closes #6353)