Changed -lcurses to -lncurses

The latest Linux distros from OpenSUSE, Fedora, and other non-Debian based distros no longer add symlinks for libcurses.so -> libncurses.so. Trying to compile menuconfig with -lcurses will not work on these distros, so I changed -lcurses to -lncurses, since -lncurses will work on any modern Linux distro with the ncurses5 libraries installed.

See http://stackoverflow.com/questions/1517756/whats-the-difference-between-lcurses-and-lncurses-when-compiling-c-using-ncur for more info.