http: fix new warnings (#6153)

vlib/net/http/backend_nix.c.v

@@ -41,7 +41,7 @@ fn (req &Request) ssl_do(port int, method Method, host_name, path string) ?Respo
 	//println(req_headers)
 	C.BIO_puts(web, req_headers.str)
 	mut content := strings.new_builder(100)
-	mut buff := [bufsize]byte
+	mut buff := [bufsize]byte{}
 	mut readcounter := 0
 	for {
 		readcounter++

vlib/net/http/backend_windows.c.v

@@ -21,5 +21,5 @@ fn (req &Request) ssl_do(port int, method Method, host_name, path string) ?Respo
 	length := int(C.request(&ctx, port, addr.to_wide(), sdata.str, &buff))
 
 	C.vschannel_cleanup(&ctx)
-	return parse_response(string(buff, length))
+	return parse_response(buff.vstring_with_len(length))
 }

vlib/net/http/http.v

@@ -410,7 +410,7 @@ pub fn escape(s string) string {
 }
 
 fn (req &Request) http_do(port int, method Method, host_name, path string) ?Response {
-	rbuffer := [bufsize]byte
+	rbuffer := [bufsize]byte{}
 	mut sb := strings.new_builder(100)
 	s := req.build_request_headers(method, host_name, path)
 	client := net.dial(host_name, port) or {