Partially solved: I get compilation error for gtkfontselhack.c when using
the win_iconv package from
http://www.gtk.org/download-windows.html or
-ansi when using the package mingw_lib_inc.zip from
http://ricardo.ecn.wfu.edu/pub/gretl/winbuild/, but not when not using
-ansi for the package mingw_lib_inc.zip.
Andreas