Enable all header fields in the compose menu to be translated.

Enable all header fields in the compose menu to be translated.

While it is suggested they need not be, for some locales it might be
preferable to be able to localize the fields.

For instance, fr_FR may want to change the punctuation to have a space
in front of the colon.  ja_JP may be more comfortable with a native
character set description of the field when using it every day.