Serious terminology confusion in r20600

I just went to review r20600 for backport, and found serious terminology
confusion - namely, the change doesn't actually have anything to do with
what the log message describes.

mailer.py has two separate concepts by which option values are processed:

 * 'maps': Defined in the [maps] section, and operate as lookup tables.
 * 'parameters': Defined by predefinition and regexp matches, and
      operate as string substitutions.

The code change in r20600 actually enables parameter substitution for
several additional parameters - which is a good change.

However, the log message repeatedly refers to 'maps' and 'mappings',
even quoting a comment from mailer.conf.example referring to mappings as
justification for the change.

I like the change, and am +1 on backporting the code to 1.4.x, but the
log message and STATUS metadata are highly misleading, and should be
fixed first.

Max.