patman: add support for omitting bouncing addresses

Add support for reading a list of bouncing addresses from a in-tree file
(doc/bounces) and from the ~/.patman config file. These addresses are
stripped from the Cc list.

Signed-off-by: Chris Packham <judge.packham@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Philipp Tomsich &lt;philipp.tomsich@theobroma-systems.com <mailto:philipp.tomsich@theobroma-systems.com&gt;>