PyGILState_STATE was added in commit 3fd6fdce (Gilnanny + pystate.pxd)
with struct type on-purpose different from what CPython actually uses
with the idea so that PyGILState_STATE cannot be coerced into int.

However as it is, it prevents PyGILState_STATE usage:

	cdef PyGILState_STATE gstate = PyGILState_Ensure()

gives

	Variable type 'PyGILState_STATE' is incomplete

Fix it by making PyGILState_STATE a defined structure.

(cherry picked from commit 82a0ed43)