Also adds one exception to linter rules:

    typedef struct {
      kvec_t(Object) stack;
    } EncodedData;

is completely valid (from the style guide point of view) code.

This removes some stack overflows in new test regarding deeply nested variables.
Now in place of crashing vim_to_object/msgpack_rpc_from_object/etc it crashes
clear_tv with stack overflow.

This ought to prevent stack overflow, but I do not see this actually working:
*lua* code crashes with stack overflow when trying to deserialize msgpack from
Neovim, Neovim is fine even if nesting level is increased 100x (though test
becomes very slow); not sure how recursive function may survive this. So it
looks like there are currently only two positive effects:

1. NULL lists are returned as empty (#4596).
2. Functional tests are slightly more fast. Very slightly. Checked for Release
   build for test/functional/eval tests because benchmarking of debug mode is
   not very useful.

Problem:    Missing change to eval.c
Solution:   Also change feedkeys().

https://github.com/vim/vim/commit/5f8a14b9dea094b8bbab94cfc1e8da8e633fbc01