Allow ':' in the subject of imported messages

[stgit] / templates / patchmail.tmpl

From: %(commname)s <%(commemail)s>
Subject: [PATCH %(patchnr)s/%(totalnr)s] %(shortdescr)s
Date: %(date)s
%(endofheaders)s
%(longdescr)s
---

%(diffstat)s

%(diff)s