st/mesa: Add R8G8B8A8_SRGB case to st_pipe_format_to_mesa_format.

With the recent SRGB changes all my automated OpenGL llvmpipe tests
(piglit, conform, glretrace) start asserting with the backtrace below.

I'm hoping this change will fix it.  I'm not entirely sure, as this
doesn't happen in my development machine (the bug probably depends on
the exact X visual).

Anyway, it seems the sensible thing to do here.

   Program terminated with signal 5, Trace/breakpoint trap.
   #0  _debug_assert_fail (expr=expr@entry=0x7fa324df2ed7 "0", file=file@entry=0x7fa324e3fc30 "src/mesa/state_tracker/st_format.c", line=line@entry=758, function=function@entry=0x7fa324e40160 <__func__.34798> "st_pipe_format_to_mesa_format") at src/gallium/auxiliary/util/u_debug.c:281
   #0  _debug_assert_fail (expr=expr@entry=0x7fa324df2ed7 "0", file=file@entry=0x7fa324e3fc30 "src/mesa/state_tracker/st_format.c", line=line@entry=758, function=function@entry=0x7fa324e40160 <__func__.34798> "st_pipe_format_to_mesa_format") at src/gallium/auxiliary/util/u_debug.c:281
   No locals.
   #1  0x00007fa3241d22b3 in st_pipe_format_to_mesa_format (format=format@entry=PIPE_FORMAT_R8G8B8A8_SRGB) at src/mesa/state_tracker/st_format.c:758
           __func__ = "st_pipe_format_to_mesa_format"
   #2  0x00007fa3241c8ec5 in st_new_renderbuffer_fb (format=format@entry=PIPE_FORMAT_R8G8B8A8_SRGB, samples=0, sw=<optimised out>) at src/mesa/state_tracker/st_cb_fbo.c:295
           strb = 0x19e8420
   #3  0x00007fa32409d355 in st_framebuffer_add_renderbuffer (stfb=stfb@entry=0x19e7fa0, idx=<optimised out>) at src/mesa/state_tracker/st_manager.c:314
           rb = <optimised out>
           format = PIPE_FORMAT_R8G8B8A8_SRGB
           sw = <optimised out>
   #4  0x00007fa32409e635 in st_framebuffer_create (st=0x19e7fa0, st=0x19e7fa0, stfbi=0x19e7a30) at src/mesa/state_tracker/st_manager.c:458
           stfb = 0x19e7fa0
           mode = {rgbMode = 1 '\001', floatMode = 0 '\000', colorIndexMode = 0 '\000', doubleBufferMode = 0, stereoMode = 0, haveAccumBuffer = 0 '\000', haveDepthBuffer = 1 '\001', haveStencilBuffer = 1 '\001', redBits = 8, greenBits = 8, blueBits = 8, alphaBits = 8, redMask = 0, greenMask = 0, blueMask = 0, alphaMask = 0, rgbBits = 32, indexBits = 0, accumRedBits = 0, accumGreenBits = 0, accumBlueBits = 0, accumAlphaBits = 0, depthBits = 24, stencilBits = 8, numAuxBuffers = 0, level = 0, visualRating = 0, transparentPixel = 0, transparentRed = 0, transparentGreen = 0, transparentBlue = 0, transparentAlpha = 0, transparentIndex = 0, sampleBuffers = 0, samples = 0, maxPbufferWidth = 0, maxPbufferHeight = 0, maxPbufferPixels = 0, optimalPbufferWidth = 0, optimalPbufferHeight = 0, swapMethod = 0, bindToTextureRgb = 0, bindToTextureRgba = 0, bindToMipmapTexture = 0, bindToTextureTargets = 0, yInverted = 0, sRGBCapable = 1}
           idx = <optimised out>
   #5  st_framebuffer_reuse_or_create (st=st@entry=0x19dfce0, fb=<optimised out>, stfbi=stfbi@entry=0x19e7a30) at src/mesa/state_tracker/st_manager.c:728
   No locals.
   #6  0x00007fa32409e8cc in st_api_make_current (stapi=<optimised out>, stctxi=0x19dfce0, stdrawi=0x19e7a30, streadi=0x19e7a30) at src/mesa/state_tracker/st_manager.c:747
           st = 0x19dfce0
           stdraw = 0x640064
           stread = 0x1300000006
           ret = <optimised out>
   #7  0x00007fa324074a20 in XMesaMakeCurrent2 (c=c@entry=0x195bb00, drawBuffer=0x19e7e90, readBuffer=0x19e7e90) at src/gallium/state_trackers/glx/xlib/xm_api.c:1194
   No locals.
   #8  0x00007fa3240783c8 in glXMakeContextCurrent (dpy=0x194e900, draw=8388610, read=8388610, ctx=0x195bac0) at src/gallium/state_trackers/glx/xlib/glx_api.c:1177
           drawBuffer = <optimised out>
           readBuffer = <optimised out>
           xmctx = 0x195bb00
           glxCtx = 0x195bac0
           firsttime = 0 '\000'
           no_rast = 0 '\000'
   #9  0x00007fa32407852f in glXMakeCurrent (dpy=<optimised out>, drawable=<optimised out>, ctx=<optimised out>) at src/gallium/state_trackers/glx/xlib/glx_api.c:1211
   No locals.

Acked-by: Brian Paul <brianp@vmware.com>

src/mesa/state_tracker/st_format.c

@@ -753,6 +753,8 @@ st_pipe_format_to_mesa_format(enum pipe_format format)
 
    case PIPE_FORMAT_B8G8R8X8_SRGB:
       return MESA_FORMAT_B8G8R8X8_SRGB;
+   case PIPE_FORMAT_R8G8B8A8_SRGB:
+      return MESA_FORMAT_B8G8R8A8_SRGB;
 
    default:
       assert(0);