qt-gstreamer update

[Diane Trout]

Hello,

David reminded me that it can be useful to ask for help.

The thing I think that needs fixing, preferably by someone with more Qt 
experience than me.

The newer gstreamer api needs you to "map" and "unmap" chunks of memory from a 
buffer in order to get at your tasty multimedia content.

While trying to get something working I basically copied the C api.

I made a copy of of the GstMapInfo class in: 
https://github.com/detrout/qt-gstreamer/blob/1.0-incomplete-patch-of-doom/src/QGst/memory.h

I added the copy because a design goal of QtGstreamer was to not need the 
development headers for GStreamer to build applications.

However I'm sure there's got to be a better solution involving a private 
::Data structure with some kind of Q.*Pointer actually holding a real 
GstMapInfo structure.

And maybe it should also save the associated Buffer so it can automatically 
unmap itself when the MapInfo goes out of scope.

If someone wants to suggest a better API in the near future I'd love to see 
it.

I've been chopping 1.0-incomplete-patch-doom up into smaller pieces in the 
1.0-proposed branch. However I may delete whats currently on that branch in 
and replace it with a reordered version.

Diane