Matrix Polling and Parent control

 - Polling for Matrix builds calculates changes based on children.

 - Parent build disabled when using "Matrix options for Perforce" in
the Matrix Configuration (can be enabled by checking the “Build parent”
box).

 - Parent Build now substitutes ${var} with ‘*’ for the workspace view.
e.g.

  //depot/${os}/… //ws/${os}/…

becomes…

  //depot/*/… //ws/*/…

instead of…

  //depot/os/… //ws/os/…