import psycopg2.submodule doesn't work with compat

[nanonyme]

Since compat only registers psycopg2 to sys.modules, importing submodules with full dotted path does not work. The approach of registering all psycopg2ct submodules in sys.modules as psycopg2 submodules is kinda ugly so I'm opening this bug in hope someone has better ideas on working around.