i965: Add support for integral vertex attributes.

i965: Add support for integral vertex attributes.

When a vertex shader input attribute is declared with an integral type
(e.g. ivec4), we need to ensure that the generated vertex shader code
addresses the vertex attribute register using the proper register
type.  (Previously, we assumed all vertex shader input attributes were
floating-point).

In addition, when uploading vertex data that was specified with
VertexAttribIPointer, we need to instruct the vertex fetch unit to
convert the data to signed or unsigned int, rather than float.  And
when filling in the implied w=1 on a vector with less than 4
components, we need to fill it in with the integer representation of 1
rather than the floating-point representation of 1.

Fixes piglit tests vs-attrib-{ivec4,uvec4}-precision.

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>