title: DoubleValidator allows to type point and comma symbols in TextInput
body: <p>I have a strange behavior of DoubleValidator in TextInput. It allows to put both comma "," and point "." symbols when I type some float number. My current locale is "en_US" and apparently validator should restrict the possibility to type the comma symbol. </p>
  
  <p>There is a simple piece of code where I can reproduce this behavior.</p>
  
  <pre><code>import QtQuick 2.9
  import QtQuick.Window 2.3
  Window {
      visible: true
      width: 640
      height: 480
      title: qsTr("Hello World")
      TextInput {
          id: inputField
          anchors.centerIn: parent
          validator: DoubleValidator { bottom: -Infinity;
              top: Infinity;
              decimals: 4;
              notation: DoubleValidator.StandardNotation }
          text: "0"
      }
  }
  </code></pre>
  
  <p>Later in code I'm trying to get number from this field</p>
  
  <pre><code>x = value ? Number.fromLocaleString(Qt.locale(), inputField.value)
  </code></pre>
  
  <p>And if I print the number with comma separator I reasonably get the warning  </p>
  
  <blockquote>
    <p>Warning: QML Error: Error: Locale: Number.fromLocaleString(): Invalid format</p>
  </blockquote>
  
  <p>and <em>x</em> holds an integer part of float number.</p>
  
  <p>I would appreciate if you can help me to understand what I'm doing wrong. My only purpose here is to correctly validate numbers with floating point depending on users locale.</p>