Add options do_108 and do_109 to make-installers.sh
Add option require_version2_signature to support 10.9.5+
Fix bug causing missing kext signatures to go unnoticed

If Gatekeeper is disabled, spctl will return exit code 0 even if
the signaure is missing or invalid. Using codesign -v works around
the false negative since it will still return a non-zero exit code
when validation fails regardless of whether Gatekeeper is disabled.