t/t9001: use egrep when regular expressions are involved

Supplying backslashed, extended regular expressions to grep is not
portable.  Use egrep instead.
Signed-off-by: NBrandon Casey <casey@nrlssc.navy.mil>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

t/t9001-send-email.sh

@@ -943,7 +943,7 @@ test_expect_success 'asks about and fixes 8bit encodings' '
 	grep "do not declare a Content-Transfer-Encoding" stdout &&
 	grep email-using-8bit stdout &&
 	grep "Which 8bit encoding" stdout &&
-	grep "Content\\|MIME" msgtxt1 >actual &&
+	egrep "Content|MIME" msgtxt1 >actual &&
 	test_cmp actual content-type-decl
 '
 
@@ -954,7 +954,7 @@ test_expect_success 'sendemail.8bitEncoding works' '
 	git send-email --from=author@example.com --to=nobody@example.com \
 			--smtp-server="$(pwd)/fake.sendmail" \
 			email-using-8bit >stdout &&
-	grep "Content\\|MIME" msgtxt1 >actual &&
+	egrep "Content|MIME" msgtxt1 >actual &&
 	test_cmp actual content-type-decl
 '
 
@@ -966,7 +966,7 @@ test_expect_success '--8bit-encoding overrides sendemail.8bitEncoding' '
 			--smtp-server="$(pwd)/fake.sendmail" \
 			--8bit-encoding=UTF-8 \
 			email-using-8bit >stdout &&
-	grep "Content\\|MIME" msgtxt1 >actual &&
+	egrep "Content|MIME" msgtxt1 >actual &&
 	test_cmp actual content-type-decl
 '