org-crypt: make org-decrypt disable auto-save-mode (configurable)
As auto-save-mode can only cause leakage when there's actual decrypted
data lying around, don't check for it (and potentially cause annoyance)
on init, but only when org-decrypt-entry is called.
* lisp/org-crypt.el:
- add defcustom `org-crypt-disable-auto-save'
- `org-decrypt-entry': before decrypting, check whether
`auto-save-mode' is enabled for the current buffer, and act
on it according to how `org-crypt-disable-auto-save' is set.
- remove comment re "encrypt[ing] Org auto-saved buffers"
- remove on-init check for `auto-save-default'