Also add a functionaltest-lua target to run the functional tests using the lua
interpreter and corresponding helper to top-level Makefile

New feature: `VTermState->mode.bracketpaste`
  Enabled by default, but note that `vterm_state_reset()` disables it.
  https://github.com/neovim/libvterm/commit/03981def6baedf459ff1539531f8a389520038fa
References #3476

New feature: `vterm_state_set_unrecognised_fallbacks`
  https://github.com/neovim/libvterm/commit/acf7f19713587df91ab9bb26c84a2c9a22ba8745

Oh, and terminal reflow works now.
Closes #2514 (but not #3864, that's a bit more tricky)

Although UNIX is a registered trademark of The Open Group, it doesn't
really matter whether we refer to these systems as UNIX, Unix, or
Unix-like. So, for consistency, refer to them collectively as Unix.

Related:
http://www.greens.org/about/unix.html
http://www.unixica.com/html/unixunix.html

Otherwise the dynamic library is built also and find_library will prefer
that over the static one. That results in linking against the dynamic
library which will not be found after install.

This code:
  https://github.com/neovim/neovim/blob/8b3c399b6d7f4a277d80da4b29349fed944f7d46/third-party/CMakeLists.txt#L130
should prevent the above problem, but it doesn't hurt to be explicit.

Point to new location.

The luajit.org download URL:
  http://luajit.org/download/LuaJIT-2.0.4.tar.gz
is breaking our travis builds because of connection problems.

So far luacheck's rockspec specified only the git protocol. Hence people
behind firewalls/proxies, that block port 9814, had trouble fetching this
dependency via luarocks.

The latest commit updated the rockspec to use either git or https. Thus common
workarounds like this are not needed anymore:

    git config --global url."https://".insteadOf git://

References #3769.

Source: https://github.com/mpeterv/luacheck
Docs:   http://luacheck.readthedocs.org/en/0.12.0/index.html

Run via "make testlint".