Fixed problem with origin for DST_COMPLEX style.
Fixed handling of DSS_DISABLED and DSS_DEFAULT styles.

Added handling of BS_MULTILINE style, label alignment
styles (BS_RIGHT, etc.) and some exotic styles BS_FLAT (only
pushbuttons for now), and BS_PUSHLIKE.

Modified label drawing procedure: now all kinds of buttons
use common BUTTON_DrawLabel function. Actual label drawing is
performed by DrawStateW function.

GroupBox must use WM_CTLCOLORSTATIC instead of WM_CTLCOLORBTN message.