docs: Replace connector building and other information by references to online docs.

Author: rsomla1

doc/building.txt

@@ -5,8 +5,8 @@ MySQL Connector/C++ is a library for applications written in C or C++ that
 communicate with MySQL database servers. Version 8.0 of Connector/C++
 implements three different APIs which can be used by applications:
 
-- The new [X DevAPI] (@ref devapi) for applications written in C++.
-- The new [X DevAPI for C] (@ref xapi) for applications written in plain C.
+- The new [X DevAPI] (@ref devapi_ref) for applications written in C++.
+- The new [X DevAPI for C] (@ref xapi_ref) for applications written in plain C.
 - The [legacy JDBC4-based API] (@ref jdbc_ref)
   also implemented in version 1.1 of the connector.
 
@@ -27,12 +27,13 @@ explained in @ref usage.
 
 More information:
 
-- [Connector/C++ X DevAPI Reference] (@ref devapi_ref)
-- [Connector/C++ X DevAPI for C Reference] (@ref xapi_ref)
+- [Connector/C++ X DevAPI Reference] (@ref devapi)
+- [Connector/C++ X DevAPI for C Reference] (@ref xapi)
 - [How to build code that uses Connector/C++](@ref usage)
-- [Building Connector/C++] (@ref building)
 - [Indexing Document Collections] (@ref indexing)
 
+See also our
+[online documentation] (https://dev.mysql.com/doc/connector-cpp/8.0/en/)
 
 <!--
   Copyright (c) 2015, 2018, Oracle and/or its affiliates. All rights reserved.