build warnings for igraph_i_set_attribute_table and g_memmove

[beenhuang]

When I installed tgen on Fedora34, I encountered the following warnings in the pictures. How should I fix the bugs?

[sporksmith]

I don't think these will cause any issues at runtime. The warnings are because the symbols are deprecated and so will likely go away in the future, which will break the build if we haven't replaced their usage by then.

From a quick look, it seems g_memmove should be replaced by memmove, and igraph_i_set_attribute_table with igraph_set_attribute_table