ncurses: change handling of PKG_CONFIG_LIBDIR

ncurses: change handling of PKG_CONFIG_LIBDIR

When PKG_CONFIG_LIBDIR was unset in the environment, the configure
script was deducing the PKG_CONFIG_LIBDIR from the location of the
pkg-config binary, which doesn't make a lot of sense, and isn't done
by other autotools based packages.

Patch imported from the Buildroot project:
https://github.com/buildroot/buildroot/blob/master/package/ncurses/0001-fixup-pkg-config-handling.patch

Also refresh patches while we're at.

Signed-off-by: Jo-Philipp Wich <jo@mein.io>