glamor: Add glamor_program based copy acceleration

Paints with textures, using a temporary buffer for overlapping copies

Performs CPU to GPU transfers for pixmaps in memory. Accelerates copy
plane when both objects are in the GPU. Includes copy_window
acceleration too.

v2: Use NV_texture_barrier for non-overlapping copies within the same
drawable

v3: Switch to glamor_make_current

v4: Do overlap check on the bounding box of the region rather than
    on individual boxes

v5: Use Eric Anholt's re-written comments which provide a more accurate
    description of the code

v6: Use floating point uniform for copy plane bit multiplier. This
    avoids an int to float conversion in the copy plane fragment shader.

    Use round() instead of adding 0.5 in copy plane. round() and +0.5
    end up generating equivalent code, and performance measurements
    confirm that they are the same speed. Round() is a bit clearer
    though, so we'll use it.

Signed-off-by: Keith Packard <keithp@keithp.com>
Reviewed-by: Eric Anholt <eric@anholt.net>
Reviewed-by: Markus Wick <markus@selfnet.de>

glamor/glamor.c

@@ -408,6 +408,8 @@ glamor_init(ScreenPtr screen, unsigned int flags)
         epoxy_has_gl_extension("GL_ARB_map_buffer_range");
     glamor_priv->has_buffer_storage =
         epoxy_has_gl_extension("GL_ARB_buffer_storage");
+    glamor_priv->has_nv_texture_barrier =
+        epoxy_has_gl_extension("GL_NV_texture_barrier");
     glGetIntegerv(GL_MAX_RENDERBUFFER_SIZE, &glamor_priv->max_fbo_size);
 #ifdef MAX_FBO_SIZE
     glamor_priv->max_fbo_size = MAX_FBO_SIZE;