Added photon map implementation from the book.

Makefile

@@ -4,9 +4,10 @@ PVDIR = PhotonViewer
 OBJECTS = main.o sampling.o camera.o environment.o disk.o plane.o sphere.o \
           phong_brdf.o hsa_brdf.o directional_light.o point_light.o \
           spot_light.o sphere_area_light.o disk_area_light.o scene.o tracer.o \
-          path_tracer.o whitted_tracer.o rgbe.o kd_tree.o photon_tracer.o
+          path_tracer.o whitted_tracer.o rgbe.o kd_tree.o photon_tracer.o \
+          photonmap.o
 DEPENDS = $(OBJECTS:.o=.d)
-CXXFLAGS = -std=c++11 -pedantic -Wall -DGLM_FORCE_RADIANS -fopenmp -DUSE_CPP11_RANDOM #-DENABLE_KD_TREE
+CXXFLAGS = -std=c++11 -pedantic -Wall -DGLM_FORCE_RADIANS -fopenmp -DUSE_CPP11_RANDOM -fno-builtin #-DENABLE_KD_TREE
 LDLIBS = -lfreeimage -ljson_spirit
 
 .PHONY: all