Get 2000/thadgavin to compile under linux

In this case fedora but presumably other linux distributions as well.
Specifically some systems need -lm for linking.

2000/thadgavin/Makefile

@@ -124,7 +124,7 @@ CFLAGS= ${CSTD} ${CWARN} ${ARCH} ${CDEFINE} ${CINCLUDE} ${OPT}
 # Libraries needed to build
 #
 #LIBS=
-LIBS= -lncurses
+LIBS= -lncurses -lm
 #LIBS= -L ${X11_LIBDIR} -lX11
 #LIBS= `${SDL2_CONFIG} --libs`