Remove Bungled warning on missing component directives

Remove Bungled warning on missing component directives

* Make Squid display a ERROR notice and ignore squid.conf directives
  which belong to components disabled at build time instead of throwing
  up 'FATAL: Bungled' message and aborting.

* Polish the 'requires X' message text for better display of cases like
  'requires MS Windows' and 'requires Linux'

* Add 'requires X' message for --enable-auth, --enable-eui, and
  --enable-ssl-crtd which were missing.