Close#635Close#668Close#539
Use a temporary batchfile for :!, system(), and jobs and run it in cmd.exe.
This bypasses Vim/Neovim issues in Windows and reduces the need to set more options.
Also, s:shellesc_cmd works in a batchfile only.
Set shellredir for system() in Windows
$SHELL sets the default value of 'shell' (see :h 'shell').
This affects shellredir but cmd.exe requires '>%s 2>&1'.