This is bug compatibility for XVideo drivers that scale the whole
picture rather than the source rectangle (the XVideo 2 specification
does not really state which behaviour is correct).

This works because the video output core only applies crop parameters
*after* the vout display plugin is activated. This is brittle though:
the A/R and crop parameters should probably be passed as configuration
like zoom.

(cherry picked from commit 4aa17707fc63c59ea173347d9b695a9a415822fe)
Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>