st/nine: Implement ps3 advanced input definition feature

ps3 allows definitions of the inputs like:
DCL_TEXCOORD0 v0.xy;
DCL_NORMAL2 v0.z;
DCL_NORMAL3 v0.w;

Nine wouldn't have handled this situation properly.

Apparently very few applications use this feature.

Signed-off-by: Axel Davy <axel.davy@ens.fr>