qt4-embedded: Allow use of Qt Media Player in multi-headed system
Qt-embedded can be used on multiple screens by using environment variables
QWS_DISPLAY, QWS_MOUSE_PROTO, et cetera.
The gstreamer element mfw_v4lsink used to accelerate media playback on i.MX
devices can also be pointed at different displays through the 'device'
property, but the current acceleration patch doesn't have a mechanism for
setting the property, and always uses the compiled-in default.
This patch allows userspace startup code to override the default through
the use of the 'v4lsinkdev' environment variable.
Please refer to the Qt4-embedded documentation for proper usage of the
QWS_x environment variables and the Freescale Multimedia documentation
for descriptions of the various gstreamer elements.
A sequence of this for a secondary display might be this:
