Fix program refcounting assertion failure during context tear-down

When purging the program hash table, the refcount _should_ be one since
the program is referenced by the hash table.  Need to explicitly set to
zero before calling delete().

Also, purge high-level shader hash tables before low-level program hash tables.

src/mesa/main/context.c

@@ -582,6 +582,8 @@ delete_program_cb(GLuint id, void *data, void *userData)
 {
    struct gl_program *prog = (struct gl_program *) data;
    GLcontext *ctx = (GLcontext *) userData;
+   ASSERT(prog->RefCount == 1); /* should only be referenced by hash table */
+   prog->RefCount = 0;  /* now going away */
    ctx->Driver.DeleteProgram(ctx, prog);
 }
 
@@ -707,6 +709,12 @@ free_shared_state( GLcontext *ctx, struct gl_shared_state *ss )
    _mesa_HashDeleteAll(ss->DisplayList, delete_displaylist_cb, ctx);
    _mesa_DeleteHashTable(ss->DisplayList);
 
+#if FEATURE_ARB_shader_objects
+   _mesa_HashWalk(ss->ShaderObjects, free_shader_program_data_cb, ctx);
+   _mesa_HashDeleteAll(ss->ShaderObjects, delete_shader_cb, ctx);
+   _mesa_DeleteHashTable(ss->ShaderObjects);
+#endif
+
 #if defined(FEATURE_NV_vertex_program) || defined(FEATURE_NV_fragment_program)
    _mesa_HashDeleteAll(ss->Programs, delete_program_cb, ctx);
    _mesa_DeleteHashTable(ss->Programs);
@@ -732,12 +740,6 @@ free_shared_state( GLcontext *ctx, struct gl_shared_state *ss )
    _mesa_HashDeleteAll(ss->ArrayObjects, delete_arrayobj_cb, ctx);
    _mesa_DeleteHashTable(ss->ArrayObjects);
 
-#if FEATURE_ARB_shader_objects
-   _mesa_HashWalk(ss->ShaderObjects, free_shader_program_data_cb, ctx);
-   _mesa_HashDeleteAll(ss->ShaderObjects, delete_shader_cb, ctx);
-   _mesa_DeleteHashTable(ss->ShaderObjects);
-#endif
-
 #if FEATURE_EXT_framebuffer_object
    _mesa_HashDeleteAll(ss->FrameBuffers, delete_framebuffer_cb, ctx);
    _mesa_DeleteHashTable(ss->FrameBuffers);