Better RFC compliance - leading dot, line endings

RFC 5321 section 4.5.2 - leading dot on a line must be doubled
RFC 5321 section 2.3.8 - all lines must end with CR-LF sequence
Added --text-encoding parameter.
Version 3.5

- New parameter --text-encoding
- Improved compliance with SMTP RFC 5321
  (suggested by Richard L Hamilton)