Add support for unbuffered streaming about webcam HOT 1 OPEN

We (gostream) also need support for an unbuffered stream, though, for different reasons. We depend on mediadevices which in turn depends on this library for its linux implementation (see camera_linux.go). mediadevices calls camera.SetBufferCount(1) when opening a camera and later camera.ReadFrame() to get a frame from that camera. Because camera.ReadFrame() returns the last frame in the buffer we always get a stale image. Setting camera.SetBufferCount(2) gives us two stale frames and so forth. Is there currently a way to get the current frame from camera.ReadFrame() rather than a previously buffered image?

from webcam.