git-am: force egrep to use correct characters set

According to egrep(1) the US-ASCII table is used when LC_ALL=C is set.
We do not rely here on the LC_ALL value we get from the environment.

Signed-off-by: Christian Himpel <chressie@gmail.com>
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

git-am.sh

@@ -205,7 +205,7 @@ check_patch_format () {
 			# and see if it looks like that they all begin with the
 			# header field names...
 			sed -n -e '/^$/q' -e '/^[ 	]/d' -e p "$1" |
-			egrep -v '^[!-9;-~]+:' >/dev/null ||
+			LC_ALL=C egrep -v '^[!-9;-~]+:' >/dev/null ||
 			patch_format=mbox
 		fi
 	} < "$1" || clean_abort