* allout.el: Increment version to 2.2.1 in file commentary.

* allout.el: Increment version to 2.2.1 in file commentary.
(allout-version): Increment to 2.2.1.
(allout-default-layout): New customization variable, used when the
file lacks a specific allout-layout.  Uses allout-layout-type for
recursively nested definition.
(allout-layout-type): Widget defining allout layouts, necessary for
self-recursive definition.
(allout-mode): Incorporate allout-default-layout as fallback for
allout-layout.
(allout-layout): Mark as 'safe-local-variable', and refer mention
fallback to `allout-default-layout' in absence of a specified value.
(allout-passphrase-verifier-string)
(allout-passphrase-hint-string): Mark as 'safe-local-variable'.
(allout-file-passphrase-verifier-string): Obsolete variable, removed.
(allout-get-encryption-passphrase-verifier): Use correct name of
passphrase verifier in docstring.

From Ken Manheimer.