title: Using QWebview gives compiling errors, but not because Qt += webkit is missing from the .pro file
body: <p>I made a project in Qt and added a QWebview to it then I added <code>Qt += webkit</code> to the <code>.pro</code> file. However, upon compiling, I get these to errors:</p>
  
  <pre><code>...ui_mainwindow.h:42: error: undefined reference to `_imp___ZN8QWebViewC1EP7QWidget'
  ...ui_mainwindow.h:45: error: undefined reference to `_imp___ZN8QWebView6setUrlERK4QUrl'
  </code></pre>
  
  <p>The errors refer to here (in <code>ui_mainwindow.h</code>):</p>
  
  <pre><code>...
      webView = new QWebView(centralWidget); // &lt;-- First error here
      webView-&gt;setObjectName(QStringLiteral("webView"));
      webView-&gt;setGeometry(QRect(0, 0, 300, 200));
      webView-&gt;setUrl(QUrl(QStringLiteral("about:blank"))); // &lt;-- Second error here
      MainWindow-&gt;setCentralWidget(centralWidget);
  ...
  </code></pre>
  
  <p>In Program.pro:</p>
  
  <pre><code>QT       += core gui webkit
  </code></pre>
  
  <p>I think those errors usually occur without <code>Qt += webkit</code>, but in this case that's not what's happening.</p>