title: Android LinearLayout - wrap_content + Split remaining space
body: <p>Consider the following layout: a horizontal LinearLayout with 2 buttons with the text "Push me", and an ImageButton with a small envelope icon (for example, to send an email).</p>
  
  <p>I want the ImageButton's width to be set to "wrap_content" so it's only as large as the envelope's size, and then I want the other two buttons to evenly split the remainder of the screen evenly. How can it be done?</p>