Trust but verify 'scutil' to return ComputerName

Apparently, it is possible to set up a Mac such that
`scutil --get ComputerName` hasn't been set.

This change checks if that fails and falls back to the original
mechanism.

Closes #2155
Closes #2183
fix missing add-zsh-hook in pygmalion.zsh-theme

Fix "command not found: add-zsh-hook" since #3053 removes `autoload -U add-zsh-hook`
Symfony2 plugin use first console found
Symfony2 plugin look for files only
Symfony2 plugin autocomplete for app/console and bin/console
Merge pull request #3087 from hacfi/symfony

Symfony2 plugin use first console found
Merge pull request #2743 from docwhat/issue-2155-scutil

Trust but verify 'scutil' to return ComputerName
Merge pull request #3072 from clippit/patch-1

Fix missing add-zsh-hook in pygmalion.zsh-theme
Merge remote-tracking branch 'origin/master' into Darwin