Complete the stub for _thread.pyi. (#2900)

Definitions based on https://docs.python.org/3/library/_thread.html.

stdlib/3/_thread.pyi

@@ -1,15 +1,31 @@
 # Stubs for _thread
 
-# NOTE: These are incomplete!
+from types import TracebackType
+from typing import Any, Callable, Dict, NoReturn, Optional, Tuple, Type
 
-from typing import Any
+error = RuntimeError
 
 def _count() -> int: ...
+
 _dangling = ...  # type: Any
 
 class LockType:
-    def acquire(self) -> None: ...
+    def acquire(self, blocking: bool = ..., timeout: float = ...) -> bool: ...
     def release(self) -> None: ...
+    def locked(self) -> bool: ...
+    def __enter__(self) -> bool: ...
+    def __exit__(
+        self,
+        type: Optional[Type[BaseException]],
+        value: Optional[BaseException],
+        traceback: Optional[TracebackType],
+    ) -> None: ...
 
+def start_new_thread(function: Callable[..., Any], args: Tuple[Any, ...], kwargs: Dict[str, Any] = ...) -> int: ...
+def interrupt_main() -> None: ...
+def exit() -> NoReturn: ...
 def allocate_lock() -> LockType: ...
 def get_ident() -> int: ...
+def stack_size(size: int = ...) -> int: ...
+
+TIMEOUT_MAX: int