Simplify conditions for superenv activation

`MacOS::Xcode.without_clt? && MacOS.sdk_path.nil?` should never be true.

In its earliest form, this would raise a bare RuntimeError in an effort
to have the bug reported. Later, it was changed to silently disable
superenv. But we don't want to do that. If there's a bug, or the user's
system is misconfigured, we want to know, so that we can fix the bug, or
the user can fix their system. So let's remove the condition.
Only directories are candidates for superenv bin
neon: always use Homebrew's openssl

We now always use Homebrew's openssl. Users can install certs by adding
.pem files to
  $(brew --prefix)/etc/openssl/certs
and then running
  $(brew --prefix openssl)/bin/c_rehash
cadaver: always use Homebrew's openssl
subversion: always use Homebrew's openssl
subversion: update 1.8.8 bottle.