Add GstMemory/GstAllocator/GstBufferPool/GstVideoBufferPool bindings
https://gstreamer.freedesktop.org/data/doc/gstreamer/head/gstreamer/html/GstMemory.html https://gstreamer.freedesktop.org/data/doc/gstreamer/head/gstreamer/html/GstAllocator.html https://gstreamer.freedesktop.org/data/doc/gstreamer/head/gstreamer/html/GstBufferPool.html
GstMemory needs to be manually generated (because miniobject). See caps.rs, tags.rs, sample.rs. Support for it needs to be added to buffer.rs.
The others should be possible to mostly autogenerate.