sys: various fixes (#3762)

* sys: simplify _getframe

* sys: mark positional-only args

* sys: fix platform availability

* sys: remove settscdump

This function is no longer documented in 3.6 and above (and doesn't
exist on master, was removed in 4fd64b9a6aba9e6e1a5d).
In 3.5 documentation it's mentioned that it's only available if Python
was compiled with a special flag:
https://docs.python.org/3.5/library/sys.html#sys.settscdump

* sys: update whitelists

stdlib/3/sys.pyi

@@ -127,7 +127,7 @@ class _version_info(Tuple[int, int, int, str, int]):
     serial: int
 version_info: _version_info
 
-def call_tracing(fn: Callable[..., _T], args: Any) -> _T: ...
+def call_tracing(__func: Callable[..., _T], __args: Any) -> _T: ...
 def _clear_type_cache() -> None: ...
 def _current_frames() -> Dict[int, Any]: ...
 def _debugmallocstats() -> None: ...
@@ -136,14 +136,14 @@ def __excepthook__(type_: Type[BaseException], value: BaseException,
                    traceback: TracebackType) -> None: ...
 def exc_info() -> _OptExcInfo: ...
 # sys.exit() accepts an optional argument of anything printable
-def exit(arg: object = ...) -> NoReturn: ...
+def exit(__status: object = ...) -> NoReturn: ...
 def getcheckinterval() -> int: ...  # deprecated
 def getdefaultencoding() -> str: ...
 if sys.platform != 'win32':
     # Unix only
     def getdlopenflags() -> int: ...
 def getfilesystemencoding() -> str: ...
-def getrefcount(arg: Any) -> int: ...
+def getrefcount(__object: Any) -> int: ...
 def getrecursionlimit() -> int: ...
 
 @overload
@@ -153,10 +153,7 @@ def getsizeof(obj: object, default: int) -> int: ...
 
 def getswitchinterval() -> float: ...
 
-@overload
-def _getframe() -> FrameType: ...
-@overload
-def _getframe(depth: int) -> FrameType: ...
+def _getframe(__depth: int = ...) -> FrameType: ...
 
 _ProfileFunc = Callable[[FrameType, str, Any], Any]
 def getprofile() -> Optional[_ProfileFunc]: ...
@@ -184,7 +181,7 @@ class _WinVersion(Tuple[int, int, int, int,
 
 def getwindowsversion() -> _WinVersion: ...  # Windows only
 
-def intern(string: str) -> str: ...
+def intern(__string: str) -> str: ...
 
 def is_finalizing() -> bool: ...
 
@@ -192,11 +189,10 @@ if sys.version_info >= (3, 7):
     __breakpointhook__: Any  # contains the original value of breakpointhook
     def breakpointhook(*args: Any, **kwargs: Any) -> Any: ...
 
-def setcheckinterval(interval: int) -> None: ...  # deprecated
-def setdlopenflags(n: int) -> None: ...  # Linux only
-def setrecursionlimit(limit: int) -> None: ...
-def setswitchinterval(interval: float) -> None: ...
-def settscdump(on_flag: bool) -> None: ...
+def setcheckinterval(__n: int) -> None: ...  # deprecated
+def setdlopenflags(__flags: int) -> None: ...  # Linux only
+def setrecursionlimit(__limit: int) -> None: ...
+def setswitchinterval(__interval: float) -> None: ...
 
 def gettotalrefcount() -> int: ...  # Debug builds only
 

tests/stubtest_whitelists/py38.txt

@@ -205,15 +205,6 @@ struct.iter_unpack
 struct.unpack
 struct.unpack_from
 sys.UnraisableHookArgs
-sys._getframe
-sys.call_tracing
-sys.exit
-sys.getrefcount
-sys.intern
-sys.setcheckinterval
-sys.setdlopenflags
-sys.setrecursionlimit
-sys.setswitchinterval
 threading.ExceptHookArgs
 time.CLOCK_PROF
 time.CLOCK_UPTIME

tests/stubtest_whitelists/py3_common.txt

@@ -757,7 +757,6 @@ sys.last_type
 sys.last_value
 sys.ps1
 sys.ps2
-sys.settscdump
 sys.tracebacklimit
 sysconfig.is_python_build
 sysconfig.parse_config_h