fixed missing header in render_to_tga and make file for non llvm users

Former-commit-id: 44d5ef9ca891d2b2a89980c15ed2444c700762e5

Makefile.conf

@@ -26,6 +26,8 @@ ifeq ($(IGL_USERNAME),ajx)
 	IGL_WITH_MATLAB=1
 	IGL_WITH_MOSEK=1
 	IGL_WITH_PNG=1
+	# I don't use llvm
+	AFLAGS=-m64
 endif
 
 ifeq ($(IGL_USERNAME),jalec_linux) 

include/igl/render_to_tga.cpp

@@ -1,5 +1,6 @@
 #include "render_to_tga.h"
 #include "tga.h"
+#include <cstdlib>
 
 IGL_INLINE bool igl::render_to_tga(
   const std::string tga_file,