Use GL instead of GLES for GL_ARB_occlusion_query support

Makefile

 endif
 
 clean: check
-	@rm -f ${NAME} ${NAME}.png ${NAME}.vert ${NAME}.frag
+	@rm -f ${NAME} ${NAME}.png
 ifneq ($(target), local)
 	@ssh $(SSH_DUT) 'rm -f ~/${NAME} ~/${NAME}.png ~/${NAME}.vert ~/${NAME}.frag'
 endif

occlusion.cc

 #include <GL/gl.h>
 #include <GL/glext.h>
 #include <GLES3/gl3.h>
-#include <GLES3/gl3ext.h>
 
 #include <fstream>
 #include <iostream>
 void InitializeEGL() {
   EGLDisplay display = eglGetDisplay(EGL_DEFAULT_DISPLAY);
   eglInitialize(display, nullptr, nullptr);
-  eglBindAPI(EGL_OPENGL_ES_API);
+  eglBindAPI(EGL_OPENGL_API);
 
   const EGLint config_attribs[] = {
       EGL_SURFACE_TYPE, EGL_DONT_CARE,

occlusion.frag

-#version 310 es
+#version 300 es
+#extension GL_EXT_separate_shader_objects : enable
 
 precision mediump float;
 

occlusion.vert

-#version 310 es
+#version 300 es
+#extension GL_EXT_separate_shader_objects : enable
 
 precision mediump float;