The tests would leave the following test files in the root directory:

    Xtest-functional-plugin-shada.shada
    Xtest-functional-plugin-shada.shada.tmp.f

Clean them up in teardown().

shada: Do not save unlisted and quickfix buffers

Replaced old unit tests for errno with libuv error codes UV_ENOENT
and UV_EEXIST (for os_open and os_getperms).

Added libuv include path to test/includes compiler calls - needed
to get hold of libuv headers.

Store last search direction when writing ShaDa files

Note: it looks like viminfo files do not store search direction intentionally.
After reading viminfo file search direction was considered to be “forward”.

Note 2: all files created on earlier Neovim version will automatically receive
“forward” direction.

Fixes #3580

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

Run via "make testlint".