coverity/71507: Unchecked return value (CHECKED_RETURN)

Don't check for err->set since object_to_vim always return false when error is set
vim-patch:7.4.433

Problem:    Test 75 fails on MS-Windows.
Solution:   Use ":normal" instead of feedkeys(). (Michael Soyka)

https://code.google.com/p/vim/source/detail?r=v7-4-433
version: Mark patch 430 NA.

Not relevant because we always compile with +conceal.
job/valgrind: Fix invalid reads/missing free.

The JobEvent structure may refer to a job after it has been freed. Apply
@tarruda's patch to extract the job data before pushing the event.

Also, fix the type, "data" -> "job", in on_job_exit() and free the job
name in the last job event.
job_start: Do not close in/out/err on error.

The streams job_close_*() reference have not been initialized by the
time we call uv_spawn() and libuv closes these pipes for us when spawn()
fails.
test/shell: Add failure tests for `system()`.
test/job: Implement some basic jobs tests.
Merge PR #1350 'valgrind/jobs: Fix invalid reads.'
api: Implement vim_command_output function

This function can be used by API clients to execute a command and capture the
output.
fix 'sign unplace id'

Since the introduction of the FOR_ALL_BUFFERS macro, 'sign unplace id'
without a buffer was only removing the sign from the first buffer rather
than all buffers, as described in the documentation.

  :help sign-unplace

--

modeline discussion: https://github.com/akkartik/neovim/commit/7863c247db#commitcomment-8342590
Merge #1342 "signs bugfix"
Merge pull request #1347 from splinterofchaos/433

vim-patch:7.4.433
fix #1027: :wundo segfault in new, non-empty buffer
input/job: process ctrl+c and do conversion in the read callback

- Extract `process_interrupts` out of `convert_input`
- Instead of waiting for os_breakcheck/os_inchar calls, call `convert_input`
  and `process_interrupts` directly from the read callback in input.c.
- Remove the `settmode` calls from `job_wait`. Now that interrupts are
  processed in the event loop, there's no need to set the terminal to cooked
  which introduces other problems(ref 7.4.427)
input: Fix sizes of input/read buffers

Input buffer must be bigger than read buffer to ensure it always has space for
converted data.
api: Add vim_input function and mark vim_feedkeys as deferred

The `vim_feedkeys` must be deferred because it can potentially free the buffer
passed to `os_inchar`(which in turns calls `vim_feedkeys` indirectly).

The new `vim_input` function can be used to emulate user input(Since it does not
mess with the typeahead, it is safe to execute without deferring).
travis: Make sure valgrind report is shown on test failures
Merge PR #1357 'Fixes to input/job modules'
fs.c: add FUNC_ATTR_NONNULL_ALL to all functions
CONTRIBUTING.md: more guidance on cosmetic changes #1346