glapi: Remove GL_SGIX_pixel_texture from the dispatch table

There is no GLX protocol for this function.  Open-source Linux driver
have not supported this extension for many years, and it seems
unlikely at this point that this support will return.  There's no
reason to have slots for this function in the dispatch table.

The unit tests (GetProcAddress::TableDidntShrink and others) are also updated.

Signed-off-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Brian Paul <brianp@vmware.com>

src/mapi/glapi/tests/check_table.cpp

@@ -84,8 +84,11 @@ TEST(GetProcAddress, TableDidntShrink)
     *
     * 6 entries were removed when GL_SGIS_pixel_texture was removed from the
     * dispatch table.
+    *
+    * 1 entry was removed when GL_SGIX_pixel_texture was removed from the
+    * dispatch table.
     */
-   EXPECT_GE(table_entries, 978u - 6u);
+   EXPECT_GE(table_entries, 978u - 6u - 1u);
 }
 
 TEST(GetProcAddress, QueriedDispatchSizeBigEnough)
@@ -1281,7 +1284,6 @@ const struct name_offset known_dispatch[] = {
    { "glFogCoorddvEXT", _O(FogCoorddvEXT) },
    { "glFogCoordfEXT", _O(FogCoordfEXT) },
    { "glFogCoordfvEXT", _O(FogCoordfvEXT) },
-   { "glPixelTexGenSGIX", _O(PixelTexGenSGIX) },
    { "glBlendFuncSeparateEXT", _O(BlendFuncSeparateEXT) },
    { "glFlushVertexArrayRangeNV", _O(FlushVertexArrayRangeNV) },
    { "glVertexArrayRangeNV", _O(VertexArrayRangeNV) },