Split stdlib into Python 2 and 3 versions (#5442)

All new files in stdlib/@python2 are straight copies of the
corresponding files in stdlib.

stdlib/@python2/webbrowser.pyi

@@ -0,0 +1,103 @@
+import sys
+from typing import Callable, List, Optional, Sequence, Text, Union
+
+class Error(Exception): ...
+
+if sys.version_info >= (3, 7):
+    def register(
+        name: Text, klass: Optional[Callable[[], BaseBrowser]], instance: Optional[BaseBrowser] = ..., *, preferred: bool = ...
+    ) -> None: ...
+
+else:
+    def register(
+        name: Text, klass: Optional[Callable[[], BaseBrowser]], instance: Optional[BaseBrowser] = ..., update_tryorder: int = ...
+    ) -> None: ...
+
+def get(using: Optional[Text] = ...) -> BaseBrowser: ...
+def open(url: Text, new: int = ..., autoraise: bool = ...) -> bool: ...
+def open_new(url: Text) -> bool: ...
+def open_new_tab(url: Text) -> bool: ...
+
+class BaseBrowser:
+    args: List[str]
+    name: str
+    basename: str
+    def __init__(self, name: Text = ...) -> None: ...
+    def open(self, url: Text, new: int = ..., autoraise: bool = ...) -> bool: ...
+    def open_new(self, url: Text) -> bool: ...
+    def open_new_tab(self, url: Text) -> bool: ...
+
+class GenericBrowser(BaseBrowser):
+    args: List[str]
+    name: str
+    basename: str
+    def __init__(self, name: Union[Text, Sequence[Text]]) -> None: ...
+    def open(self, url: Text, new: int = ..., autoraise: bool = ...) -> bool: ...
+
+class BackgroundBrowser(GenericBrowser):
+    def open(self, url: Text, new: int = ..., autoraise: bool = ...) -> bool: ...
+
+class UnixBrowser(BaseBrowser):
+    raise_opts: Optional[List[str]]
+    background: bool
+    redirect_stdout: bool
+    remote_args: List[str]
+    remote_action: str
+    remote_action_newwin: str
+    remote_action_newtab: str
+    def open(self, url: Text, new: int = ..., autoraise: bool = ...) -> bool: ...
+
+class Mozilla(UnixBrowser):
+    remote_args: List[str]
+    remote_action: str
+    remote_action_newwin: str
+    remote_action_newtab: str
+    background: bool
+
+class Galeon(UnixBrowser):
+    raise_opts: List[str]
+    remote_args: List[str]
+    remote_action: str
+    remote_action_newwin: str
+    background: bool
+
+class Chrome(UnixBrowser):
+    remote_args: List[str]
+    remote_action: str
+    remote_action_newwin: str
+    remote_action_newtab: str
+    background: bool
+
+class Opera(UnixBrowser):
+    remote_args: List[str]
+    remote_action: str
+    remote_action_newwin: str
+    remote_action_newtab: str
+    background: bool
+
+class Elinks(UnixBrowser):
+    remote_args: List[str]
+    remote_action: str
+    remote_action_newwin: str
+    remote_action_newtab: str
+    background: bool
+    redirect_stdout: bool
+
+class Konqueror(BaseBrowser):
+    def open(self, url: Text, new: int = ..., autoraise: bool = ...) -> bool: ...
+
+class Grail(BaseBrowser):
+    def open(self, url: Text, new: int = ..., autoraise: bool = ...) -> bool: ...
+
+if sys.platform == "win32":
+    class WindowsDefault(BaseBrowser):
+        def open(self, url: Text, new: int = ..., autoraise: bool = ...) -> bool: ...
+
+if sys.platform == "darwin":
+    class MacOSX(BaseBrowser):
+        name: str
+        def __init__(self, name: Text) -> None: ...
+        def open(self, url: Text, new: int = ..., autoraise: bool = ...) -> bool: ...
+    class MacOSXOSAScript(BaseBrowser):
+        def __init__(self, name: Text) -> None: ...
+        def open(self, url: Text, new: int = ..., autoraise: bool = ...) -> bool: ...