bring ncurses to /usr/lib, /usr/include/ncurses

link with -lncurses, no need to compile rpaths to software anymore
link ncurses with rpath PREFIX/gnu/lib

Put auxiliary libs generated by the build (lib{menu,panel,form}) in
PREFIX/gnu/lib and ncurses in PREFIX/lib; this way other programs will
be able to link with -lncurses without having to specify rpath (unless
they also link with the auxiliary libraries)