mesa: Correct the is_vertex_position decision for dlists.

We have to use _mesa_inside_dlist_begin_end instead of
_mesa_inside_begin_end to see if we are inside a glBegin/glEnd block in
case of display lists.
So split the is_vertex_position function used in vertex attribute processing
into a imm and dlist variant and use the appropriate _mesa_inside_begin_end
variant.

Reviewed-by: Brian Paul <brianp@vmware.com>
Signed-off-by: Mathias Fröhlich <Mathias.Froehlich@web.de>

src/mesa/vbo/vbo_exec_api.c

@@ -457,6 +457,20 @@ vbo_exec_begin_vertices(struct gl_context *ctx)
 }
 
 
+/**
+ * If index=0, does glVertexAttrib*() alias glVertex() to emit a vertex?
+ * It depends on a few things, including whether we're inside or outside
+ * of glBegin/glEnd.
+ */
+static inline bool
+is_vertex_position(const struct gl_context *ctx, GLuint index)
+{
+   return (index == 0 &&
+           _mesa_attr_zero_aliases_vertex(ctx) &&
+           _mesa_inside_begin_end(ctx));
+}
+
+
 /**
  * This macro is used to implement all the glVertex, glColor, glTexCoord,
  * glVertexAttrib, etc functions.