Comment out non-git git prompt include, add zsh parameters that were being included by that script, and adjust the git git prompt to check for ZSH version
Squashed 'zsh/zsh-syntax-highlighting/' content from commit e5d8a50

git-subtree-dir: zsh/zsh-syntax-highlighting
git-subtree-split: e5d8a50d362a153a28506be6fae9cf179dbb5fd4
Merge commit '6f343bd323a22f523e1f26e5fa17f7010159904b' as 'zsh/zsh-syntax-highlighting'
Add conditional sourcing of zsh-syntax-highlighting