All these files should be sourced, not executed; and Debian's lintian complains:
W: zsh-syntax-highlighting: script-not-executable usr/share/zsh-syntax-highlighting/zsh-syntax-highlighting.zsh
This was broken by c2b9327b0763f3457fb09db17e22ee9e1e024792
and tracked as zsh-users/zsh-syntax-highlighting#199.
This fixes the vanilla-newline.zsh test, which was was (consciously) broken
by the previous commit.