Fix broken functional test.

In Lua, all math is floating point.  We need to coerce the result of a
division into a integer with the `{get,set}_height` and
`{get,set}_width` window_spec functional tests.
build: print the error result when the tests fail

Any diagnostic information is useful when things fail.  In my case, it
printed out the fact that the tests were segfaulting.
deps: Update bundled lua client version

The new version fixes defunct processes which causes random test failures on
some systems(#1519)
Merge PR #1547 'Update bundled lua client version'
Add missing refcount increment for systemlist()

- get_system_output_as_rettv() was missing a refcount increment when
  returning an empty list, i.e. when there was no output
- we now use rettv_list_aloc() instead of list_alloc()
- issue #1530
Merge pull request #1552 from equalsraf/tb-fix-1530

add missing refcount increment for systemlist()
Merge pull request #1543 from jszakmeister/fix-broken-functional-tests

Fix broken functional test.
build: add failure message along with number in GenerateHelptags.cmake
Merge pull request #1544 from jszakmeister/run-tests-error-code

build: print the error result when the tests fail
build: probe the compiler to see if we need to turn down _FORTIFY_SOURCE

Some builds don't use Release (such as Gentoo, though it can be told
to).  So let's go a bit further and probe the compiler to see if we need
to turn down the _FORTIFY_SOURCE level.
Merge pull request #1514 from jszakmeister/better-fortify-detection

build: probe the compiler to see if we need to turn down _FORTIFY_SOURCE
Improve Python host messages.
Merge pull request #1559 from fwalch/python-messages

Improve Python host messages.
Remove crypto

Closes https://github.com/neovim/docs/pull/26