- Add support for TBSTYLE_EX_HIDECLIPPEDBUTTONS.
- Replace 'magic numbers' with #define'd constants.
- Fix TBN_INITCUSTOMIZE.
- Add support for TBN_CUSTHELP and TBN_RESET.
- Fix TB_SETEXTENDEDSTYLE (it appears it should or the new style,
  rather than set).
- Fix TB_SETSTYLE (this is meant to be for setting the control style,
  not the button style).