Tweak MacOS X Makefile for likely scenario

examples/opengl_example/Makefile.Macosx

@@ -5,7 +5,8 @@
 #
 
 CXXFLAGS=-framework OpenGL -framework Cocoa -framework IOKit 
-#CXXFLAGS+=-L/usr/local/Cellar/glew/1.10.0/lib -L/usr/local/Cellar/glfw3/3.0.4/lib
+CXXFLAGS+=-I/usr/local/Cellar/glew/1.10.0/include -I/usr/local/Cellar/glfw3/3.0.4/include
+CXXFLAGS+=-L/usr/local/Cellar/glew/1.10.0/lib -L/usr/local/Cellar/glfw3/3.0.4/lib
 CXXFLAGS+=-lglew -lglfw3
 CXXFLAGS+=-I../../
 CXXFLAGS+= -D__APPLE__