sendmail: don't mangle e-mail headers

Leave the original To: and Cc: headers untouched, when we try to extract
addresses from them.

Signed-off-by: Aaro Koskinen <aaro.koskinen@iki.fi>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/mailutils/sendmail.c b/mailutils/sendmail.c
index 4f73512..0f536ad 100644
--- a/mailutils/sendmail.c
+++ b/mailutils/sendmail.c
@@ -299,7 +299,9 @@
 		// To: or Cc: headers add recipients
 		if (opts & OPT_t) {
 			if (0 == strncasecmp("To:", s, 3) || 0 == strncasecmp("Bcc:" + 1, s, 3)) {
-				rcptto(sane_address(s+3));
+				char *r = xstrdup(s+3);
+				rcptto(sane_address(r));
+				free(r);
 				goto addheader;
 			}
 			// Bcc: header adds blind copy (hidden) recipient