extension EXT_gpu_shader4
+# Buffer textures have their own extension
+optional GL_SAMPLER_BUFFER_EXT
+optional GL_INT_SAMPLER_BUFFER_EXT
+optional GL_UNSIGNED_INT_SAMPLER_BUFFER_EXT
+# Ditto for rectangular textures
+optional GL_INT_SAMPLER_2D_RECT_EXT
+optional GL_UNSIGNED_INT_SAMPLER_2D_RECT_EXT