* Move PyEval_SaveThread to GNATCOLL.Python.Eval
* Move PyEval_RestoreThread to GNATCOLL.Python.Eval
* Move PyThreadState to GNATCOLL.Python
* Remove binding to PyEval_InitThreads (not needed since 3.7)
* Remove Has_Thread_Support (we assume python 3 always have thread
support)
Part of S821-014
Change-Id: I037b19be518a36600663df20d34f233c91bc4139