Fix for TextBoxes not moving text

When moving the carat or adding characters that exceed the textbox's visible space, the text did not change its position, although the carat did.

The fix:
- Adds empty PostLayout() in TextBox class to avoid Label's PostLayout
  from being called. Otherwise the text's position will always be set to
  a fixed position defined by the alignment.

Misc changes:
- Removed extraneous semicolon in TextBox::MakeCaratVisible()
- Added newline in TextBox.cpp to avoid GNU compiler warnings