sys-process/latencytop: Fix build with recent ncurses

sys-process/latencytop: Fix build with recent ncurses

...because the `tinfow` was not getting linked:

  x86_64-pc-linux-gnu-gcc -O2 -pipe -march=native -ggdb
  -Wno-sign-compare -Wl,-O1 -Wl,--as-needed latencytop.o text_display.o
  translate.o fsync.o -o latencytop `x86_64-pc-linux-gnu-pkg-config
  --libs glib-2.0` -lncursesw
  /usr/lib/gcc/x86_64-pc-linux-gnu/4.9.3/../../../../x86_64-pc-linux-gnu/bin/ld:
  text_display.o: undefined reference to symbol 'curs_set'
  /lib64/libtinfow.so.6: error adding symbols: DSO missing from command line
Closes: https://github.com/gentoo/gentoo/pull/3028