mesa: Remove misc pbuffer attributes from struct gl_config

pbuffers aren't a first-class object in mesa, they're just funnily-named
framebuffers. It's thus somewhat silly to track this state separately
when it's effectively identical to GL_MAX_RENDERBUFFER_SIZE, and there's
never been a DRI driver that's ever set these values to anything
interesting. Drop them from mesa (but leave the tokens defined for
compatibility).

Reviewed-by: Eric Anholt <eric@anholt.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/9817>

src/mesa/drivers/dri/common/utils.c

@@ -421,7 +421,6 @@ __DRIconfig **driConcatConfigs(__DRIconfig **a,
     return all;
 }
 
-/* careful, lack of trailing semicolon */
 #define __ATTRIB(attrib, field) case attrib: *value = config->modes.field; break
 
 /**
@@ -489,11 +488,11 @@ driGetConfigAttribIndex(const __DRIconfig *config,
     __ATTRIB(__DRI_ATTRIB_GREEN_MASK,			greenMask);
     __ATTRIB(__DRI_ATTRIB_BLUE_MASK,			blueMask);
     __ATTRIB(__DRI_ATTRIB_ALPHA_MASK,			alphaMask);
-    __ATTRIB(__DRI_ATTRIB_MAX_PBUFFER_WIDTH,		maxPbufferWidth);
-    __ATTRIB(__DRI_ATTRIB_MAX_PBUFFER_HEIGHT,		maxPbufferHeight);
-    __ATTRIB(__DRI_ATTRIB_MAX_PBUFFER_PIXELS,		maxPbufferPixels);
-    __ATTRIB(__DRI_ATTRIB_OPTIMAL_PBUFFER_WIDTH,	optimalPbufferWidth);
-    __ATTRIB(__DRI_ATTRIB_OPTIMAL_PBUFFER_HEIGHT,	optimalPbufferHeight);
+    case __DRI_ATTRIB_MAX_PBUFFER_WIDTH:
+    case __DRI_ATTRIB_MAX_PBUFFER_HEIGHT:
+    case __DRI_ATTRIB_MAX_PBUFFER_PIXELS:
+    case __DRI_ATTRIB_OPTIMAL_PBUFFER_WIDTH:
+    case __DRI_ATTRIB_OPTIMAL_PBUFFER_HEIGHT:
     case __DRI_ATTRIB_VISUAL_SELECT_GROUP:
         *value = 0;
         break;

src/mesa/main/mtypes.h

@@ -192,13 +192,6 @@ struct gl_config
    GLint sampleBuffers;
    GLuint samples;
 
-   /* SGIX_pbuffer / GLX 1.3 */
-   GLint maxPbufferWidth;
-   GLint maxPbufferHeight;
-   GLint maxPbufferPixels;
-   GLint optimalPbufferWidth;   /* Only for SGIX_pbuffer. */
-   GLint optimalPbufferHeight;  /* Only for SGIX_pbuffer. */
-
    /* OML_swap_method */
    GLint swapMethod;