git-send-email: skip RFC2047 quoting for ASCII subjects
The git-send-email always use RFC2047 subject quoting for
files with "broken" encoding - non-ASCII files without
Content-Transfer-Encoding, even for ASCII subjects. This is
harmless but unnecessarily ugly for people reading the raw
headers. This patch skips rfc2047 quoting when the subject
does not need it.
Signed-off-by: Krzysztof Mazur <krzysiek@podlesie.net> Signed-off-by: Jeff King <peff@peff.net>