GL Renderer in Weston

The GL renderer in Weston creates an eglImage from a dma-buf object that it receives with Linux DMA-BUF Unstable V1 Protocol using the EGL_EXT_image_dma_buf_import and EGL_EXT_image_dma_buf_import_modifiers extensions. Weston obtains the GL texture target to be used with this eglImage by calling eglQueryDmaBufModifiersEXT(), and binds the eglImage to the texture.