ilo: initialize constant buffer SURFACE_STATE early

Fix ilo_gpe_init_view_surface_for_buffer to allow buffer to be NULL, and add
ilo_gpe_set_view_surface_bo to set it later.  This allows us to set up
SURFACE_STATE early for constant buffers backed by user buffers.
glsl/ast: Check that geometry shader interface block inputs are arrays.
glsl/ast: Fix assertion failure when GS input declared as non-array.

Previously, if a geometry shader input was declared as a non-array, we
would flag the proper compiler error, but then before we got a chance
to report it to the client, handle_geometry_shader_input_decl() would
assertion fail.

With this patch, handle_geometry_shader_input_decl() ignores
non-arrays.
glsl/ast: Don't perform GS input array checks on non-inputs.

Previously, we were accidentally calling
handle_geometry_shader_input_decl() on non-input interface block
declarations, resulting in bogus error checking.
!UPSTREAM: glsl: lower gl_ClipDistanceIn to gl_ClipDistanceInMESA in lower_clip_distance

This corresponds to the lowering of gl_ClipDistance to gl_ClipDistanceMESA.
It converts the 2D array gl_ClipDistanceIn from EXT/ARB_geometry_shader4 to
a 1D array of vec4s, gl_ClipDistanceInMESA.

v2 (Paul Berry <stereotype441@gmail.com>): Fix indexing order for
gl_ClipDistanceIn lowering.  Properly lower bulk assignment of
gl_ClipDistanceIn[i].

TODO: May need to rework for GLSL 1.50.
!UPSTREAM: glsl/linker: Fail if linking geometry shader with 0 GEOMETRY_VERTICES_OUT.

ARB_geometry_shader4 spec 2.15.2:
"Linking will also fail [...] if the program object contains objects to form a
geometry shader, and the value of GEOMETRY_VERTICES_OUT_ARB is zero."

Reviewed-by: Paul Berry <stereotype441@gmail.com>

TODO: May not be necessary for GLSL 1.50 style geometry shaders.  Make a test to validate.
!UPSTREAM: mesa: fix transform feedback when a geometry shader is active

TODO: test
!UPSTREAM: Fix up GS handling of gl_ClipDistance/gl_ClipVertex linkage rules.

TODO:
- Test
- Squash
!UPSTREAM: make stuff safe to include from C++

TODO:
- Split
i965: Initialize all elements of ctx->ShaderCompilerOptions

Otherwise any GS that requires lowering (e.g. one that uses
gl_ClipDistance or gl_ClipDistanceIn) will fail to work.
i965: Stop including brw_vs.h from brw_vec4.h

This is backwards from what we are going to want in the long term, which is:

- brw_vec4.h declares general-purpose vec4 infrastructure needed by
  both VS and GS
- brw_vs.h includes brw_vec4.h and adds VS-specific parts.
- brw_gs.h includes brw_vec4.h and adds GS-specific parts.

Note that at the moment brw_vec.h contains a fair amount of
VS-specific declarations--I plan to address that in a later patch.
!UPSTREAM: i965/vec4: Allow for dispatch_grf_start_reg to vary.

Both 3DSTATE_VS and 3DSTATE_GS have a dispatch_grf_start_reg control,
which determines the register where the hardware delivers data sourced
from the URB (push constants followed by per-vertex input data).

For vertex shaders, we always set dispatch_grf_start_reg to 1, since
R1 is always the first register available for push constants in vertex
shaders.

For geometry shaders, we'll need the flexibility to set
dispatch_grf_start_reg to different values depending on the behvaiour
of the geometry shader; if it accesses gl_PrimitiveIDIn, we'll need to
set it to 2 to allow the primitive ID to be delivered to the thread in
R1.

This patch eliminates the assumption that dispatch_grf_start_reg is
always 1.  In vec4_visitor, we record the regnum that was passed to
vec4_visitor::setup_uniforms() in prog_data for later use.  In
vec4_generator, we consult this value when converting an abstract
UNIFORM register to a concrete hardware register.  And in the code
that emits 3DSTATE_VS, we set dispatch_grf_start_reg based on the
value recorded in prog_data.

This will allow us to set dispatch_grf_start_reg to the appropriate
value when compiling geometry shaders.  Vertex shaders will continue
to always use a dispatch_grf_start_reg of 1.

TODO:
- Move into the proper part of the series.
!UPSTREAM: i965/vec4: Virtualize setup_payload instead of setup_attributes
i965: Add brw->geometry_program
!UPSTREAM: i965: Combine 4 boolean args of brw_urb_WRITE into a flags bitfield.

The arguments to brw_urb_WRITE() were getting pretty unwieldy, and we
have to add more flags to support geometry shaders anyhow.

Also plumb these flags through brw_clip_emit_vue(),
brw_set_urb_message(), and the vec4_instruction class.

TODO:
- Test on Gen4-6
!UPSTREAM: i965: Add an opcode for doing a URB write with an offset from a register (needed for GS).

TODO
- Rename generate_gs_urb_write (and corresponding opcode) to generate_urb_write_override_r0 OSOTS
!UPSTREAM: i965: Add GS_OPCODE_THREAD_END

TODO:
- Verify that I'm returning the correct value from implied_mrf_writes() for this new opcode.
i965/gs: Add GS_OPCODE_SET_WRITE_OFFSET
i965/gs: Add GS_OPCODE_SET_VERTEX_COUNT
!UPSTREAM: i965/gs: add GS visitors