patchbomb: reST syntax for literal blocks in help text

Merge with crew-stable

mq: Parse commit message after we find start of changeset patch patch.extract extracts just the message below HG changeset patch. So to not parse comments above the patch, we reset the message if we find a changeset patch as we know the commit message comes after the changeset patch data. This is similar to the behavior of patch.extract. The drawback of this approach, after a qref -e the comment above HG changeset patch is gone. Without this patch the message would become part of the commit message in the HG changset patch part.