make text in about box selectable (fixes #1055)

src/qt/forms/aboutdialog.ui

@@ -52,6 +52,9 @@
          <property name="text">
           <string>&lt;b&gt;Bitcoin&lt;/b&gt; version</string>
          </property>
+         <property name="textInteractionFlags">
+          <set>Qt::LinksAccessibleByMouse|Qt::TextSelectableByKeyboard|Qt::TextSelectableByMouse</set>
+         </property>
         </widget>
        </item>
        <item>
@@ -62,6 +65,9 @@
          <property name="textFormat">
           <enum>Qt::RichText</enum>
          </property>
+         <property name="textInteractionFlags">
+          <set>Qt::LinksAccessibleByMouse|Qt::TextSelectableByKeyboard|Qt::TextSelectableByMouse</set>
+         </property>
         </widget>
        </item>
        <item>
@@ -93,6 +99,9 @@ This product includes software developed by the OpenSSL Project for use in the O
        <property name="wordWrap">
         <bool>true</bool>
        </property>
+       <property name="textInteractionFlags">
+        <set>Qt::LinksAccessibleByMouse|Qt::TextSelectableByKeyboard|Qt::TextSelectableByMouse</set>
+       </property>
       </widget>
      </item>
      <item>