Fix for TextBoxes not moving the text in text boxes when moving the
carat or adding characters that exceed the textbox's visible space.

- 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