Replace gl_geom_attrib enum with gl_varying_slot.

This patch makes the following search-and-replace changes:

gl_geom_attrib -> gl_varying_slot
GEOM_ATTRIB_* -> VARYING_SLOT_*
GEOM_BIT_* -> VARYING_BIT_*

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Eric Anholt <eric@anholt.net>
Tested-by: Brian Paul <brianp@vmware.com>

src/mesa/main/context.c

@@ -349,7 +349,6 @@ dummy_enum_func(void)
    gl_texture_index ti = TEXTURE_2D_ARRAY_INDEX;
    gl_vert_attrib va = VERT_ATTRIB_POS;
    gl_varying_slot vs = VARYING_SLOT_POS;
-   gl_geom_attrib ga = GEOM_ATTRIB_POSITION;
    gl_geom_result gr = GEOM_RESULT_POS;
 
    (void) bi;
@@ -359,7 +358,6 @@ dummy_enum_func(void)
    (void) ti;
    (void) va;
    (void) vs;
-   (void) ga;
    (void) gr;
 }