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'
Remove broken rvm handling in mri ruby checker

RVM does not always provide an executable for  specific ruby version
that is loaded (the "system" version).

RVM, or whatever else the user uses, should always setup "ruby" to point
to the correct version so this can always be used.
rst: extract a temp var to a query
add an faq RE setting which checkers to use
first round of updates to the doc

* remove the changelog, credits and (outdated) doc on writing syntax
  checkers
* doc the `syntastic#makeprg#build()` options
* doc how to select which syntax checkers to use
Added explicit call of escript

Added explicit call of escript, to run check, bypassing shell (actual for Windows)
Merge pull request #496 from mixvin/patch-1

Added explicit call of escript
twig: use syntastic#makeprg#build
add an faq about option names changing and remove changelog from readme
readme: fix a couple of typos
vala: remove the option to disable it

This can be done with:

`let g:syntastic_mode_map={'passive_filetypes': 'vala'}` or by setting
`let g:syntastic_vala_checkers=[]`

Closes #502.
coffeelint: remove unused and unneeded coffelint args option
Drop g:syntastic_perl_perlcritic_options.

This variable has been rendered obsolete by the standard mechanism
of g:syntastic_perl_perlcritic_args.
Modeline for help.
Update syntax_checkers/dart/dart_analyzer.vim
Don't pass -fno-code to ghc
Change the endif on SyntaxCheckers_objc_gcc_IsAvailable to endfunction