facebook/three20 — pull request #755 by aporat (2012-01-20 22:22:08+00:00)
Title: TTTableView shadow crash fix

`TTTableView` with shadows (`self.showTableShadows = YES`) will cause a crash under iOS 5 when the user tries to scroll inside the table.

This crash happens because the `layoutSubviews` function tries to use the shadow layer after the layer was already removed and released. This is an issue in iOS 5, because layers are automatically released when `removeFromSuperlayer` is called.

The fix creates a new shadow layer after the original shadow layer is released and removed. Generally, a layer shouldn't be used after `removeFromSuperlayer` is called.

Closes #733 as well.