v0.9.23

PythonCall v0.9.23

Diff since v0.9.22

Merged pull requests:

• Update GIL.jl lock's documentation (possible mistake?) (#538) (@camilodlt)
• fix PyNULL typo (#544) (@ericphanson)

Closed issues:

• Dropping GIL when calling Julia from Python (JuliaCall) (#343)
• V0.9.22 bug: error in running finalizer: UndefVarError(var=:PYNULL) (#543)