Non-strict line interpolation and rasterization

Non-strict line interpolation and rasterization

Firstly non-strict line rasterization (parallelogram decomposed to
triangles) is changed to use the TriangleInterpolator do determine
interpolated colours. Line endpoint attributes are duplicated to the
end vertices of parallelogram lines, which means that interpolation is
not along the normal of the line, but would be parallel to the major
axis.

For the interpolation to be calculated correctly by the
TriangleInterpolator, the triangle geometry needed to be produced with
the correct w values from the line endpoints, previously the triangle
was generated pre-projected with 1.0 for the W-coordinates. The
perspective interpolation previously was calculated separately using
the original line parameters passed to MultisampleLineInterpolator.

The second part of the change is to allow for a non-strict line 'GLES'
centric relaxation - GLES specified 1px non-antialiased lines would use
the 'diamond-exit' rule to produce bresenham lines. Vulkan only
specified parallelograms, but not all GLES implementations are able
to disable the 1px bresenham behaviour.

All changes are in verifyMultisameplLineGroupInterpolation and
verifyMultisameplLineGroupInterpolationInternal. Strict lines are not
affected.

This fixes Imaginations 1.2.2.x failures in:

	dEQP-VK.rasterization.flatshading*line*
	dEQP-VK.rasterization.interpolation*line*

Affects:

dEQP-VK.rasterization*line*
dEQP-GLES2.functional.rasterization*line*
dEQP-GLES3.functional.rasterization*line*

Components: Framework

VK-GL-CTS Issue: 2274

Change-Id: I0cfd496969512bdbf9d0156ea8f43e737c44512f