git am: accept patches downloaded from GMane

GMane has this wonderful feature that you can download the raw mails,
but the mails do not fully conform to the mbox format, as they do not
start with a "From ..." line.

But they start with another tell tale we can easily detect.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

git-am.sh

@@ -176,7 +176,7 @@ check_patch_format () {
 		read l2
 		read l3
 		case "$l1" in
-		"From "* | "From: "*)
+		"From "* | "From: "* | "Path:news.gmane.org"*)
 			patch_format=mbox
 			;;
 		'# This series applies on GIT commit'*)