Bug 45975

Change the title, since this issue also existed on Gen4 platforms.

Fixed by the following commit:

----
commit 43af02ac731dac7d80f7e47feb0c80e4da156769
Author: Yuanhan Liu <yuanhan.liu@linux.intel.com>
Date:   Mon Feb 27 15:46:32 2012 +0800

    i965: handle gl_PointCoord for Gen4 and Gen5 platforms
    
    This patch add the support of gl_PointCoord gl builtin variable for
    platform gen4 and gen5(ILK).
    
    Unlike gen6+, we don't have a hardware support of gl_PointCoord, means
    hardware will not calculate the interpolation coefficient for you.
    Instead, you should handle it yourself in sf shader stage.
    
    But badly, gl_PointCoord is a FS instead of VS builtin variable, thus
    it's not included in c.vue_map generated in VS stage. Thus the current
    code doesn't aware of this attribute. And to handle it correctly, we
    need add it to c.vue_map manually to let SF shader generate the needed
    interpolation coefficient for FS shader. SF stage has it's own copy of
    vue_map, thus I think it's safe to do it manually.
    
    Since handling gl_PointCoord for gen4 and gen5 platforms is somehow a
    little special, I added a lot of comments and hope I didn't overdo it ;)
    
    v2: add a /* _NEW_BUFFERS */ comment to note the state flag dependency
        and also add the _NEW_BUFFERS dirty mask (Eric).
    
    Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=45975
    Piglit: glsl-fs-pointcoord and fbo-gl_pointcoord
    
    NOTE: This is a candidate for stable release branches.
    
    Signed-off-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>
    Reviewed-by: Eric Anholt <eric@anholt.net>