#10 use fltk-config for libs

[Neil T. Spring]

LIBS = `fltk-config --use-glut --ldflags`

allows a build on OS X, where that command line expands to
nasty stuff you don't want to hard code yourself, like: -L/usr/
local/lib -lfltk_gl -framework AGL -framework OpenGL -lfltk
-framework Carbon -framework ApplicationServices
-lsupc++

Please update the Makefile to use fltk-config. My fltk is
1.1.4, and xdiskusage 1.46. LDLIBS is further unnecessary;
I don't need to link X to use fltk when it targets carbon
directly.

thanks,
-neil

[Bill Spitzak]

Makefile updated to use fltk-config.