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