* No need to restore &wfw and &wfh when using popup window

Co-authored-by: lacygoill <lacygoill@lacygoill.me>
Co-authored-by: Junegunn Choi <junegunn.c@gmail.com>

Fix #2038 

s///r is only available since perl 5.14. The Perl oneliner
was changed to work with older Perls, possibly even with 5.000.

Fix #2001

* Add RuboCop Minitest extension
* Improve error messages
* Use chomp option

Make sure that `extldflags` is quoted so that LDFLAGS containing spaces won't break the build command.

Close #1994

Close #1949

Support both ordinary completion trigger and empty trigger

    kill <tab>
    kill foo**<tab>

Close #1988
Close #385

Close #1986

Fix #1973
Fix #1974
Fix #1975

Co-authored-by: Junegunn Choi <junegunn.c@gmail.com>

Since we don't know in advance which flags tmux will support, simply
allow a single uppercase character ([A-Z]) for now.

    fzf-tmux -xR -yS
    fzf-tmux -x R -y S

Fix #1956

e.g.

  if exists('$TMUX')
    let g:fzf_layout = { 'tmux': '-p90%,60%' }
  else
    let g:fzf_layout = { 'window': { 'width': 0.9, 'height': 0.6 } }
  endif

The following code works in zsh 5.8 but not in 5.4

  ${(Q)${(Z+n+)FZF_TMUX_OPTS:--d${FZF_TMUX_HEIGHT:-40%}}}

Related: https://github.com/tmux/tmux/issues/1282

Requires latest tmux built from source (e.g. brew install tmux --HEAD)

Examples:

  # 50%/50% width and height on the center of the screen
  fzf-tmux -p

  # 80%/80%
  fzf-tmux -p80%

  # 80%/40%
  fzf-tmux -p80%,40%

  # Separate -w and -h
  fzf-tmux -w80% -h40%

  # 80%/40% at position (0, 0)
  fzf-tmux -w80% -h40% -x0 -y0

You can configure key bindings and fuzzy completion to open in tmux
popup window like so:

  FZF_TMUX_OPTS='-p 80%'

Invoking fzf from an existing Vim popup terminal is a special case.
It requires some new code to avoid E994 from being raised and the user
being stuck in a non-closable popup window.

Fix #1916

At the top of each zsh file options are set to their
standard values (those marked with <Z> in `man zshoptions`)
and `aliases` option is disabled.

At the bottom of the file the original options are restored.

Fix #1938 

Close #1940
Related: #1363 #749 #270 #49 #88 #492 #600

Fix #1926

Close #1652

To make it easier to write more complex fzf options. Although this
does not break backward compatibility, users are encouraged to update
their code accordingly.

  # Before
  _fzf_complete "FZF_ARG1 FZF_ARG2..." "$@" < <(
    # Print candidates
  )

  # After
  _fzf_complete FZF_ARG1 FZF_ARG2... -- "$@" < <(
    # Print candidates
  )

Co-authored-by: Junegunn Choi <junegunn.c@gmail.com>

Separate Unix & Windows code into platform specific files for light renderer

- https://travis-ci.org/junegunn/fzf/jobs/659496745#L676

Related #1900

This change allows the completion system of bash and zsh to return
before the input process completes.

Related #1887