MEDIUM: streams: Add a way to replay failed 0rtt requests.

Add a new keyword for retry-on, 0rtt-rejected. If set, we will try to
replay requests for which we sent early data that got rejected by the
server.
If that option is set, we will attempt to use 0rtt if "allow-0rtt" is set
on the server line even if the client didn't send early data.
diff --git a/src/proxy.c b/src/proxy.c
index 6e804a9..e3d59dc 100644
--- a/src/proxy.c
+++ b/src/proxy.c
@@ -541,6 +541,8 @@
 			curpx->retry_type |= PR_RE_503;
 		else if (!strcmp(args[i], "504"))
 			curpx->retry_type |= PR_RE_504;
+		else if (!strcmp(args[i], "0rtt-rejected"))
+			curpx->retry_type |= PR_RE_EARLY_ERROR;
 		else if (!strcmp(args[i], "none")) {
 			if (i != 1 || *args[i + 1]) {
 				memprintf(err, "'%s' 'none' keyworld only usable alone", args[0]);