glsl: Disallow vectorization of vector_insert/extract.

glsl: Disallow vectorization of vector_insert/extract.

vector_insert takes a vector, a scalar location, and a scalar value,
and produces a new vector with that component updated.  As such, it
can't be vectorized properly.

vector_extract takes a vector and a scalar location, and returns
that scalar component of the vector.  Vectorization doesn't really
make any sense.

Treating both as horizontal operations makes sure the vectorizer
won't try to touch these.

Found by inspection.

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Matt Turner <mattst88@gmail.com>