WNDO: fix truncation of {256,0,0} to {0,0,0}, which would turn red to black.

Doesn't normally matter as the screen's ideal palette is set
immediately afterwards in init_screen, in pjhigh/scrninit.c.
WNDO: make assignments in conditionals more explicit.
WNDO: suppress uninitialised 'wasin' warning.

wasin is only relevant when the window is not hidden.
WNDO: suppress uninitialised 'clickoset' warning.

clickoset is only relevant when tbox->clicks != NULL.
WNDO: suppress uninitialised 'extray' warning.

extray is only relevant when tbox->extratext != NULL.