plugins: add support for EGLImage memory outputs
Submitted by Gwenole Beauchesne @gb
Link to original bug (#743849)
Description
Add support for video/x-raw(memory:EGLImage) outputs from vaapidecode or vaapipostproc so that simple downstream elements could directly provide a bufferpool of EGLImage, or absorb EGLImage from VA decoders or video processors.