Word splitting issues resolved

Example of the issue on zsh with autocd turned on:

    ~/directory % cat <<!
    subdir1
    subdir2
    subdir3
    !
    [the output of cat]
    ~/directory/subdir1 %

The cwd has changed due to the heredoc lines being incorrectly split.

Another, much more threatening example:

    ~/ % ls
    [the directory is empty]
    ~/ % cat <<!
    touch newfile
    !
    [the output of cat]
    ~/ % ls
    newfile

It actually may lead to unintentional code execution.