kconfig: optionally use pkg-config to detect ncurses libs

When building ncurses with --with-termlib several symbols get moved from
libncurses.so to libtinfo.so. Thus when linking with libncurses.so, one
additionally needs to link with libtinfo.so.

The ncurses pkg-config module will be used to detect the necessary libs for
linking. If not available the old way of directly specifying libs will be
used.

Signed-off-by: Justin Lecher <jlec@gentoo.org>
[yann.morin.1998@free.fr: fix typo: '-ncurses' --> '-lncurses']
Tested-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>