Make mg_connect_{http,ws} use mg_parse_uri

Remove the specialized URI parser, clean up code a bit.

Fix parsing of URIs with IPv6 hosts (http://[2001:2:3::4]:567/)

PUBLISHED_FROM=968ad97585d928123106ce3828920ee073113f83

docs/c-api/util.h/mg_basic_auth_header.md

@@ -3,7 +3,8 @@ title: "mg_basic_auth_header()"
 decl_name: "mg_basic_auth_header"
 symbol_kind: "func"
 signature: |
-  void mg_basic_auth_header(const char *user, const char *pass, struct mbuf *buf);
+  void mg_basic_auth_header(const struct mg_str user, const struct mg_str pass,
+                            struct mbuf *buf);
 ---
 
 Generate a Basic Auth header and appends it to buf.