goocanvas: replace sample scalability-demo by GI
Merge pull request #157 from myokoym/goocanvas-replace-sample-scalability-demo-by-gi

goocanvas: replace sample scalability-demo by GI

Patch by Masafumi Yokoyama. Thanks!!!
gstreamer: support Gst::Bus#set_handler

But it causes SEGV... We should not use GVL lock/unlock?

[ruby-gnome2-devel-ja]

Reported by Takashi Nakajima. Thanks!!!
gstreamer: extract common code
gstreamer: sample streams/stream-status
gstreamer: sample streams fix typo
gstreamer: sample streams fix typo