V4 IR: change datastructures for dominator calculations.

Replace hashes from basic-block to basic-block with vectors that
associate basic-block index to basic-block index.

Change-Id: I834ea3d825e4d2b02c075b1b0f080f5a65f41317
Reviewed-by: Fawzi Mohamed <fawzi.mohamed@digia.com>
V4: re-enable test cases disabled for QTBUG-34047

Task-number: QTBUG-34047

Change-Id: Idcce254f3594e1f7021705704dbe6a2330aa7e65
Reviewed-by: Lars Knoll <lars.knoll@digia.com>
V4 IR: do not add unconditional jumps to work lists

Both type inference and the optimization pass do not do anything with
unconditional jumps. So, instead of adding them to the worklist and
later on removing them again, it’s faster to never add them in the first
place.

Change-Id: Ib81d43e9ea6df2b1a70e9dd1e9b9c29cb6d345d2
Reviewed-by: Lars Knoll <lars.knoll@digia.com>
V4: remove class field in DominatorTree that was used only once.

Calculation of all the children of nodes in the dominator tree is now
calculated as a local variable right before computing the dominator
frontier. The effect is that they are not retained after their only use.

Change-Id: I83c962c691b78cb767708eb04cf30d3b7a760deb
Reviewed-by: Lars Knoll <lars.knoll@digia.com>