Fix E855 on :lclose

Since 7.3.449 trying to :lclose inside BufWinLeave result in E855:

    $ vi -u /dev/null --noplugin -N
    :autocmd BufWinLeave * if empty(&bt) | lclose | endif
    :lexpr(':1:msg') | lopen | wincmd p | lclose
    E855: Autocommands caused command to abort

    $ vi -u /dev/null --noplugin -N
    :autocmd BufWinLeave * if empty(&bt) | lclose | endif
    :lexpr(':1:msg') | lopen | wincmd p | q
    E855: Autocommands caused command to abort

Another issue with this autocmd is &bt in BufWinLeave may be different from
the buffer being unloaded (this is documented behaviour for BufWinLeave).
Replacing &bt with getbufvar(0+expand('<abuf>'), '&bt') solve this, but
doesn't fix issue with E855 completely (first of above examples with
:lclose is fixed, but second with :q is not fixed).

So, to work around E855 I've changed way to close location-list:
instead of closing it on BufWinLeave, it's closed on BufEnter into
location-list window if it's only buffer in current window.
Merge branch 'master' into E855-on-lclose
Fix flake8 error/warning checking

Error/warning checking did not correctly parse output from flake8. This
resulted in Syntastic incorrectly displaying some warnings as errors.
Merge remote-tracking branch 'scrooloose/master'
use mix for elixir
Add highlight groups for the signs and the lines.

This allows users to customize the coloring of Syntastic's signs, and
also provides them a way to highlight the entire line using :sign's
linehl feature.  It preserves the current default behavior of using
the error and todo highlight groups if the customized ones aren't
present.  If the linehl group doesn't exist, then it's the same as not
specifying one, so no special highlighting for the line will occur.
always return list
Add support for buffer-local b:syntastic_checkers var.
Merge pull request #1 from xandox/use_mix_for_elixir

Use mix for elixir
Add a check for the error messages variable so that users can specify their own error format.
This allows the overrides to work
remove unused function (because of 2519d83)
New checker for TeX / LaTeX: ChkTeX.
Update help file for b:syntastic_checkers
Merge pull request #532 from dbarnett/per_buffer

Add support for buffer-local b:syntastic_checkers var.
Merge pull request #537 from brendanjerwin/fix_coffeelint_options

Fix CoffeeLint parameter overrides
Typo: Check for puppet-lint, not puppet
Merge pull request #547 from docwhat/puppet-lint

Typo: Check for puppet-lint, not puppet
Fix syntax highlighting.

The variable force_highlight_callback is gone.

Highlight functions are now consistently named
SyntaxCheckers_<filetype>_<checker>_GetHighlightRegex(), and they
take precedence over highlighting based on column.
Merge pull request #540 from lcd047/chktex

New checker for TeX / LaTeX: ChkTeX.