Disable "fast_gil" support in Py3<3.6 since Py3<3.5.2 lacks...

Disable "fast_gil" support in Py3<3.6 since Py3<3.5.2 lacks _PyThreadState_UncheckedGet() and crashes when calling PyThreadState_GET() without a thread state.

Cython/Utility/ModuleSetupCode.c

@@ -71,6 +71,8 @@
   #define CYTHON_UNPACK_METHODS 0
   #undef CYTHON_FAST_THREAD_STATE
   #define CYTHON_FAST_THREAD_STATE 0
+  #undef CYTHON_FAST_GIL
+  #define CYTHON_FAST_GIL 0
   #undef CYTHON_FAST_PYCALL
   #define CYTHON_FAST_PYCALL 0
   #undef CYTHON_PEP489_MULTI_PHASE_INIT
@@ -114,6 +116,8 @@
   #endif
   #undef CYTHON_FAST_THREAD_STATE
   #define CYTHON_FAST_THREAD_STATE 0
+  #undef CYTHON_FAST_GIL
+  #define CYTHON_FAST_GIL 0
   #undef CYTHON_FAST_PYCALL
   #define CYTHON_FAST_PYCALL 0
   #undef CYTHON_PEP489_MULTI_PHASE_INIT
@@ -169,6 +173,10 @@
   #ifndef CYTHON_FAST_THREAD_STATE
     #define CYTHON_FAST_THREAD_STATE 1
   #endif
+  #ifndef CYTHON_FAST_GIL
+    // Py3<3.5.2 does not support _PyThreadState_UncheckedGet().
+    #define CYTHON_FAST_GIL (PY_MAJOR_VERSION < 3 || PY_VERSION_HEX >= 0x03060000)
+  #endif
   #ifndef CYTHON_FAST_PYCALL
     #define CYTHON_FAST_PYCALL 1
   #endif
@@ -1339,6 +1347,8 @@ __Pyx_FastGilFuncInit();
 /////////////// FastGil.proto ///////////////
 //@proto_block: utility_code_proto_before_types
 
+#if CYTHON_FAST_GIL
+
 struct __Pyx_FastGilVtab {
   PyGILState_STATE (*Fast_PyGILState_Ensure)(void);
   void (*Fast_PyGILState_Release)(PyGILState_STATE oldstate);
@@ -1373,6 +1383,14 @@ static void __Pyx_FastGilFuncInit(void);
   #endif
 #endif
 
+#else
+#define __Pyx_PyGILState_Ensure PyGILState_Ensure
+#define __Pyx_PyGILState_Release PyGILState_Release
+#define __Pyx_FastGIL_Remember()
+#define __Pyx_FastGIL_Forget()
+#define __Pyx_FastGilFuncInit()
+#endif
+
 /////////////// FastGil ///////////////
 //@requires: CommonStructures.c::FetchCommonPointer
 // The implementations of PyGILState_Ensure/Release calls PyThread_get_key_value
@@ -1382,6 +1400,8 @@ static void __Pyx_FastGilFuncInit(void);
 // To make optimal use of this thread local, we attempt to share it between
 // modules.
 
+#if CYTHON_FAST_GIL
+
 #define __Pyx_FastGIL_ABI_module "_cython_" CYTHON_ABI
 #define __Pyx_FastGIL_PyCapsuleName "FastGilFuncs"
 #define __Pyx_FastGIL_PyCapsule \
@@ -1487,3 +1507,5 @@ static void __Pyx_FastGilFuncInit(void) {
     __Pyx_FastGilFuncInit0();
   }
 }
+
+#endif