docs(lib): fix several broken links throughout docs

Closes #1749
Closes #1750

src/client/connect/dns.rs

@@ -2,9 +2,9 @@
 //!
 //! This module contains:
 //!
-//! - A [`GaiResolver`](GaiResolver) that is the default resolver for the
+//! - A [`GaiResolver`](dns::GaiResolver) that is the default resolver for the
 //!   `HttpConnector`.
-//! - The [`Resolve`](Resolve) trait and related types to build a custom
+//! - The [`Resolve`](dns::Resolve) trait and related types to build a custom
 //!   resolver for use with the `HttpConnector`.
 use std::{fmt, io, vec};
 use std::error::Error;

src/client/mod.rs

@@ -3,7 +3,7 @@
 //! There are two levels of APIs provided for construct HTTP clients:
 //!
 //! - The higher-level [`Client`](Client) type.
-//! - The lower-level [conn](conn) module.
+//! - The lower-level [`conn`](client::conn) module.
 //!
 //! # Client
 //!