Add T to ISO8601 format.

Since we have been accepting ISO8601 without timezone up until now,
continue doing so until 4.0 EOL.

Based on 60c98eb0 by Federico G. Schwindt.

bin/varnishtest/tests/m00020.vtc

@@ -28,6 +28,9 @@ client c1 {
 	txreq -hdr "X-Date: Mon Dec 20 00:00:00 2010"
 	rxresp
 	expect resp.http.x-past == 1
+	txreq -hdr "X-Date: 2030-12-20 00:00:00"
+	rxresp
+	expect resp.http.x-future == 1
 	txreq -hdr "X-Date: 2030-12-20T00:00:00"
 	rxresp
 	expect resp.http.x-future == 1

lib/libvarnish/vtim.c

@@ -115,7 +115,8 @@ static const char *fmts[] = {
 	"%a, %d %b %Y %T GMT",	/* RFC 822 & RFC 1123 */
 	"%A, %d-%b-%y %T GMT",	/* RFC 850 */
 	"%a %b %d %T %Y",	/* ANSI-C asctime() */
-	"%F %T",		/* ISO 8601 */
+	"%F %T",		/* ISO 8601 (incorrect, only in 4.0) */
+	"%FT%T",		/* ISO 8601 */
 	NULL
 };
 

lib/libvmod_std/vmod_std_conversions.c

@@ -222,7 +222,7 @@ vmod_time2real(const struct vrt_ctx *ctx, VCL_TIME t)
 }
 
 VCL_TIME __match_proto__(td_std_time)
-vmod_time(VRT_CTX, VCL_STRING p, VCL_TIME d)
+vmod_time(const struct vrt_ctx *ctx, VCL_STRING p, VCL_TIME d)
 {
 	double r;