MINOR: http: Add support for http 413 status

Add 413 http "payload too large" status code. This will allow 413 to be
used in deny_status and errorfile.
diff --git a/src/http.c b/src/http.c
index b798c5d..7278cad 100644
--- a/src/http.c
+++ b/src/http.c
@@ -165,6 +165,7 @@
 	[HTTP_ERR_407] = 407,
 	[HTTP_ERR_408] = 408,
 	[HTTP_ERR_410] = 410,
+	[HTTP_ERR_413] = 413,
 	[HTTP_ERR_421] = 421,
 	[HTTP_ERR_425] = 425,
 	[HTTP_ERR_429] = 429,
@@ -249,6 +250,14 @@
 	"\r\n"
 	"<html><body><h1>410 Gone</h1>\nThe resource is no longer available and will not be available again.\n</body></html>\n",
 
+	[HTTP_ERR_413] =
+	"HTTP/1.1 413 Payload Too Large\r\n"
+	"Content-length: 106\r\n"
+	"Cache-Control: no-cache\r\n"
+	"Content-Type: text/html\r\n"
+	"\r\n"
+	"<html><body><h1>413 Payload Too Large</h1>\nThe request entity exceeds the maximum allowed.\n</body></html>\n",
+
 	[HTTP_ERR_421] =
 	"HTTP/1.1 421 Misdirected Request\r\n"
 	"Content-length: 104\r\n"
@@ -351,6 +360,7 @@
 	case 407: return HTTP_ERR_407;
 	case 408: return HTTP_ERR_408;
 	case 410: return HTTP_ERR_410;
+	case 413: return HTTP_ERR_413;
 	case 421: return HTTP_ERR_421;
 	case 425: return HTTP_ERR_425;
 	case 429: return HTTP_ERR_429;