Incompatible with python with threads disabled.

[Aaron Black]

I'm running a python/C++ code on a large HPC machine, and we build python with threading disabled.

(--without-threads)

Using pybindgen results in multiple errors like:

'PyEval_ThreadsInitialized' was not declared in this scope

This call is not available when threading is turned off at compile time in python.

This call is coming from:
pybindgen/typehandlers/base.py

I updated the line 'NO_GIL_LOCKING = False' to True in line 546. Is this the correct behavior? It gets me past this issue.

I wasn't sure if there is a Python CAPI call to query whether or not threading is enabled, and that query could be put around the PyEval call above.