Major refactoring.
1. Rewrite the pixmap texture uploading and downloading functions.
   Add some new functions for both the prepare/finish access and
   the new performance feature dynamic texture uploading, which
   could download and upload the current image to/from a private
   texture/fbo. In the uploading or downloading phase, we need to
   handle two things:
   The first is the yInverted option, If it set, then we don't need
   to flip y. If not set, if it is from a dynamic texture uploading
   then we don't need to flip either if the current drawing process
   will flip it latter. If it is from finish_access, then we must
   flip the y axis.

   The second thing is the alpha channel hanlding, if the pixmap's
   format is something like x8a8r8g8, x1r5g5b5 which means it doesn't
   has alpha channel, but it do has those extra bits. Then we need to
   wire those bits to 1.

2. Add almost all the required picture format support.
   This is not as trivial as it looks like. The previous implementation
   only support GL_a8,GL_a8r8g8b8,GL_x8r8g8b8. All the other format,
   we have to fallback to cpu. The reason why we can't simply add those
   other color format is because the exists of picture. one drawable
   pixmap may has one or even more container pictures. The drawable pixmap's
   depth can't map to a specified color format, for example depth 16 can
   mapped to r5g6b5, x1r5g5b5, a1r5g5b5, or even b5g6r5. So we can't get
   get the color format just from the depth value. But the pixmap do not
   has a pict_format element. We have to make a new one in the pixmap
   private data structure. Reroute the CreatePicture to glamor_create_picture
   and then store the picture's format to the pixmap's private structure.

   This is not an ideal solution, as there may be more than one pictures
   refer to the same pixmap. Then we will have trouble. There is an example
   in glamor_composite_with_shader. The source and mask often share the
   same pixmap, but use different picture format. Our current solution is to
   combine those two different picture formats to one which will not lose any
   data. Then change the source's format to this new format and then upload
   the pixmap to texture once. It works. If we fail to find a matched new
   format then we fallback.

   There still is a potential problem, if two pictures refer to the same
   pixmap, and one of them destroy the picture, but the other still remained
   to be used latter. We don't handle that situation currently. To be fixed.

3. Dynamic texture uploading.
   This is a performance feature. Although we don't like the client to hold
   a pixmap data to shared memory and we can't accelerate it. And even worse,
   we may need to fallback all the required pixmaps to cpu memory and then
   process them on CPU. This feature is to mitigate this penalty. When the
   target pixmap has a valid gl fbo attached to it. But the other pixmaps are
   not. Then it will be more efficient to upload the other pixmaps to GPU and
   then do the blitting or rendering on GPU than fallback all the pixmaps to CPU.
   To enable this feature, I experienced a significant performance improvement
   in the Game "Mines" :).

4. Debug facility.
   Modify the debug output mechanism. Now add a new macro:
   glamor_debug_output(_level_, _format_,...) to conditional output some messages
   according to the environment variable GLAMOR_DEBUG. We have the following
   levels currently.
    exports GLAMOR_DEBUG to 3 will enable all the above messages.

5. Changes in pixmap private data structure.
   Add some for the full color format supports and relate it to the pictures which
   already described. Also Add the following new elements:
   gl_fbo - to indicates whether this pixmap is on gpu only.
   gl_tex - to indicates whether the tex is valid and is containing the pixmap's
            image originally.
   As we bring the dynamic pixmap uploading feature, so a cpu memory pixmap may
   also has a valid fbo or tex attached to it. So we will have to use the above
   new element to check it true type.

After this commit, we can pass the rendercheck testing for all the picture formats.
And is much much fater than fallback to cpu when doing rendercheck testing.

Signed-off-by: Zhigang Gong <zhigang.gong@linux.intel.com>