When it is compiled, require 'bbdb or define `bbdb-buffer-name' to

When it is compiled, require 'bbdb or define `bbdb-buffer-name' to
avoid compiler warning.
(mime-method-to-display-caesar): Abolish unused local variable; avoid
problem of `mime-text-insert-decoded-body'.
Use `eval-buffer' to eval contents of
`mime-acting-situation-examples-file'.