Signed-off-by: Diego Biurrun <diego@biurrun.de>

The failures on various architectures and compilers on the RGB(A)
tests seem to have been because of one-off YCbCr->RGB conversion
results. This should make the conversion results match on most if
not all code paths.
Signed-off-by: Anton Khirnov <anton@khirnov.net>

For some reason, the prerequisites have to be specified like this.
Make works in mysterious ways.
Signed-off-by: Mans Rullgard <mans@mansr.com>

Signed-off-by: Anton Khirnov <anton@khirnov.net>

This allows fate to run without errors with or without SAMPLES
being set.
Signed-off-by: Mans Rullgard <mans@mansr.com>

This makes only tests actually using avconv depend on it.
The remaining tests already depend on what they need.
Signed-off-by: Mans Rullgard <mans@mansr.com>