GIL-free compatibility

[tranvansang]

The official document (https://webwareforpython.github.io/DBUtils/main.html) mentions "thread-safe" several times. These statements probably written with the GIL assumption. At least, I could not find any mention of the GIL on the document.

PooledDB (pooled_db) The class PooledDB in the module dbutils.pooled_db implements a pool of steady, thread-safe cached connections to a database which are transparently reused, using any DB-API 2 database module.

Do these statements hold with the GIL removal? If yes, will the doc likely be updated with the declaration of GIL mention and thread-safetiness in future updates?