title: Encoding=ASCII; and Encoding=UNICODE; do not work in an Npgsql 3 connection string
body: <p>I have a new install of PostgreSQL  (9.6.1) using the Big SQL installer, and a new install of Npgsql (3.2.0) using the .msi installer, but non-ASCII character support seems to be broken.</p>
  
  <p>My connection string is:</p>
  
  <pre><code>&lt;add name="Northwind" connectionString="Database=Northwind;Server=localhost;Port=5432;User Id=postgres;Password=123;Encoding=ASCII;" providerName="Npgsql"/&gt;
  </code></pre>
  
  <p>I get exception messages like this, when reading back non-ASCII character data:</p>
  
  <pre><code>System.Text.DecoderFallbackException : Unable to translate bytes [C3] at index 22 from specified code page to Unicode.
  </code></pre>
  
  <p>I have tried using <code>Encoding=UNICODE;</code> instead, but neither works.</p>