sys_thread_info.patch:
 - Replace threading._info() by sys.thread_info: it now always have 3 values, but all values are optional (can be None). sys.thread_info.name is None if Python is compiled without threads.
 - Reorder sys internal doc (Static objects) and replace "dict" by "struct sequence" for float_info
 - Rename _PyThread_Info() to PyThread_GetInfo() (consistent name with PyFloat_GetInfo() and PyLong_GetInfo())
 - Always compile thread.c, but add #ifdef WITH_THREAD around most the file (except PyThread_GetInfo())

Example:

>>> sys.thread_info
sys.thread_info(name='pthread', lock='semaphore', version='NPTL 2.11.2')