procps-ng: fix/patch wrong ncursesw headers assumption

The configure script/code assumes ncursesw headers live in
/usr/include/ncursesw.
That's a distribution-ism where they want to have both versions for
ABI/API compatibility, but not the case for embedded where that's not a
concern.
Hence kill the hard-coding and use pkg-config to find this out instead
of the half-made effort about it.
Fixes:
http://autobuild.buildroot.net/results/97d/97dc7f238457609c861c24f81b556973f5dec9c1/



Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Tested-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>