Dear all!
On making Gretl (gui2) about.o requires several files

from /usr/include/gtk-3.0/ 
Some files are moved to /usr/include/gtk-3.0/gdk/deprecated/, e.g. gdkcolor.h
and to /usr/include/gtk-3.0/gtk/deprecated/ e.g. gtkmisc.h
As a result, make ends with non-zero exit status.
I use Debian/jessie
Oleg
!