Testing on py39 thru py312 (on pg12 thru pg17)

I know py311 and py312 break some regression tests, but, this shows our intention to keep up with the latest Python's & Elephants

Author: luss

README.md

@@ -2,7 +2,7 @@
 Multicorn2
 ==========
 
-Multicorn Python3 Wrapper for Postgresql Foreign Data Wrapper.  Tested on Linux w/ Python 3.9-3.10 & Postgres 12-16.
+Multicorn Python3 Foreign Data Wrapper (FDW) for Postgresql.  Tested on Linux w/ Python 3.9-3.12 & Postgres 12-17.
 
 The Multicorn Foreign Data Wrapper allows you to fetch foreign data in Python in your PostgreSQL server.