Fix compilation errors in cookie_jar branch

This commit fixes multiple compilation errors introduced by the refactoring:

1. Added missing http_client_conn_free() helper function
2. Fixed cookie_jar reference (cookie_jar->count to client->cookie_jar.count)
3. Restored missing HTTP_ClientConn fields: handle, client, and url
4. Fixed undefined 'conn' variable in http_client_get_builder (changed to 'i')
5. Fixed incorrect field reference (entry.domain.len to domain.len)
6. Added missing closing parenthesis in should_send_cookie
7. Removed duplicate 'path' variable declaration
8. Fixed cookie jar access to use builder.client instead of conn->client
9. Fixed byte_queue_write calls to use .ptr and .len instead of HTTP_String structs
10. Fixed missing -> operators in url_to_connect_target
11. Fixed undefined 'url' variable by using conn->url
12. Fixed headers[i].value to set_cookie.value in save_one_cookie
13. Fixed typo: antry to entry
14. Fixed save_one_cookie parameter type (headers[i] instead of headers[i].value)
15. Fixed print_bytes calls to create HTTP_String structs
16. Added logic to store socket handle when connection is established
17. Updated http_client_get_builder signature to return HTTP_RequestBuilder
18. Updated simple_client.c example to match new API

chttp.h

@@ -878,6 +878,12 @@ typedef struct HTTP_Client HTTP_Client;
 typedef struct {
     HTTP_ClientConnState state;
 
+    // Handle to the socket
+    SocketHandle handle;
+
+    // Pointer back to the client
+    HTTP_Client *client;
+
     // Generation counter for request builder validation
     uint16_t gen;
 
@@ -893,6 +899,9 @@ typedef struct {
     HTTP_String domain;
     HTTP_String path;
 
+    // Parsed URL for connection establishment
+    HTTP_URL url;
+
     // Data received from the server
     ByteQueue input;
 
@@ -965,15 +974,8 @@ typedef struct {
     uint16_t gen;
 } HTTP_RequestBuilder;
 
-// Create a new request builder object. If the response
-// pointer is NULL, a brand new builder is created. If
-// response isn't NULL (and http_free_response wasn't
-// called on it yet), the connection associated to that
-// previous exchange is reused. Note that it's up to the
-// user to make sure the requests are targeting the same
-// host. Returns 0 on success, -1 on error.
-int http_client_get_builder(HTTP_Client *client,
-    HTTP_Response *response, HTTP_RequestBuilder *builder);
+// Create a new request builder object.
+HTTP_RequestBuilder http_client_get_builder(HTTP_Client *client);
 
 // TODO: comment
 void http_request_builder_set_user(HTTP_RequestBuilder builder, void *user);