caddyfile: Improve Dispenser.NextBlock() to support nesting

modules/caddyhttp/fileserver/caddyfile.go

@@ -43,7 +43,7 @@ func parseCaddyfile(h httpcaddyfile.Helper) (caddyhttp.MiddlewareHandler, error)
 			return nil, h.ArgErr()
 		}
 
-		for h.NextBlock() {
+		for h.NextBlock(0) {
 			switch h.Val() {
 			case "hide":
 				fsrv.Hide = h.RemainingArgs()

modules/caddyhttp/fileserver/matcher.go

@@ -69,7 +69,7 @@ func (MatchFile) CaddyModule() caddy.ModuleInfo {
 //
 func (m *MatchFile) UnmarshalCaddyfile(d *caddyfile.Dispenser) error {
 	for d.Next() {
-		for d.NextBlock() {
+		for d.NextBlock(0) {
 			switch d.Val() {
 			case "root":
 				if !d.NextArg() {