Use getwininfo() for checking quickfix window
Use getwininfo() for checking quickfix window

Since Vim8 we have win_getid() and getwininfo() functions to get
information about the current window. So we can use those functions to
find out, whether the current window is a quickfix or location list
window.

This avoids using a redir() over the :ls command and trying to
manually match the string quickfix and should be faster and also be more
robust, as the redir may fail if done recursively.

fixes #1319

unphased/vim-airline,HarmtH/vim-airline,tschundler/dotfiles,bling/vim-airline,yzhou61/vim-airline,dalguji/vim-airline,rchicoli/vim-airline,chrisbra/vim-airline,tschundler/dotfiles,tschundler/dotfiles