vf_deshake: rename Transform.vector to Transform.vec to avoid compiler confusion

The token 'vector' is a keyword in the Vector/SIMD Multimedia Extension data types and thus should not be used as a variable name.

This fixes building on powerpc/ppc64el.

Signed-off-by: Andreas Cadhalpun <Andreas.Cadhalpun@googlemail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>