In Windows Property Sheet can have any mix of icon-less tabs and tabs
with icons.  Adds a check to see if the icon we're adding is non-NULL
(otherwise random junk from memory can be rendered) when the application
has specified the PSP_USEICONID flag is set.  Changes to the Tab control
to only render icons for tabs that have the TCIF_IMAGE flag set
(previously, if the flag was set the entire image list of icons was
rendered).

Stephane Lussier <stephane@macadamian.com>
Fixes for some tab control bugs

Henning Hoffmann
Fixed some width problem with OWNERDRAW tab.

Luc Tourangeau <luc@macadamian.com>
TCM_ADJUSTRECT is now returning consistant compare to Windows.

Serge Ivanov <sergei@corel.ca>
Fixed problem with tab selection. When you select tab it becames first
visible tab. Now leftmost visible tab is calculated properly.
- Added code for correct handling of updown control.
- Forced recalculation of tabs' coordinates when:
a) all items are deleted,
b) window style is canged