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/calendar.pyi

@@ -0,0 +1,124 @@
+import datetime
+import sys
+from time import struct_time
+from typing import Any, Iterable, List, Optional, Sequence, Tuple, Union
+
+_LocaleType = Tuple[Optional[str], Optional[str]]
+
+class IllegalMonthError(ValueError):
+    def __init__(self, month: int) -> None: ...
+    def __str__(self) -> str: ...
+
+class IllegalWeekdayError(ValueError):
+    def __init__(self, weekday: int) -> None: ...
+    def __str__(self) -> str: ...
+
+def isleap(year: int) -> bool: ...
+def leapdays(y1: int, y2: int) -> int: ...
+def weekday(year: int, month: int, day: int) -> int: ...
+def monthrange(year: int, month: int) -> Tuple[int, int]: ...
+
+class Calendar:
+    firstweekday: int
+    def __init__(self, firstweekday: int = ...) -> None: ...
+    def getfirstweekday(self) -> int: ...
+    def setfirstweekday(self, firstweekday: int) -> None: ...
+    def iterweekdays(self) -> Iterable[int]: ...
+    def itermonthdates(self, year: int, month: int) -> Iterable[datetime.date]: ...
+    def itermonthdays2(self, year: int, month: int) -> Iterable[Tuple[int, int]]: ...
+    def itermonthdays(self, year: int, month: int) -> Iterable[int]: ...
+    def monthdatescalendar(self, year: int, month: int) -> List[List[datetime.date]]: ...
+    def monthdays2calendar(self, year: int, month: int) -> List[List[Tuple[int, int]]]: ...
+    def monthdayscalendar(self, year: int, month: int) -> List[List[int]]: ...
+    def yeardatescalendar(self, year: int, width: int = ...) -> List[List[int]]: ...
+    def yeardays2calendar(self, year: int, width: int = ...) -> List[List[Tuple[int, int]]]: ...
+    def yeardayscalendar(self, year: int, width: int = ...) -> List[List[int]]: ...
+    if sys.version_info >= (3, 7):
+        def itermonthdays3(self, year: int, month: int) -> Iterable[Tuple[int, int, int]]: ...
+        def itermonthdays4(self, year: int, month: int) -> Iterable[Tuple[int, int, int, int]]: ...
+
+class TextCalendar(Calendar):
+    def prweek(self, theweek: int, width: int) -> None: ...
+    def formatday(self, day: int, weekday: int, width: int) -> str: ...
+    def formatweek(self, theweek: int, width: int) -> str: ...
+    def formatweekday(self, day: int, width: int) -> str: ...
+    def formatweekheader(self, width: int) -> str: ...
+    def formatmonthname(self, theyear: int, themonth: int, width: int, withyear: bool = ...) -> str: ...
+    def prmonth(self, theyear: int, themonth: int, w: int = ..., l: int = ...) -> None: ...
+    def formatmonth(self, theyear: int, themonth: int, w: int = ..., l: int = ...) -> str: ...
+    def formatyear(self, theyear: int, w: int = ..., l: int = ..., c: int = ..., m: int = ...) -> str: ...
+    def pryear(self, theyear: int, w: int = ..., l: int = ..., c: int = ..., m: int = ...) -> None: ...
+
+def firstweekday() -> int: ...
+def monthcalendar(year: int, month: int) -> List[List[int]]: ...
+def prweek(theweek: int, width: int) -> None: ...
+def week(theweek: int, width: int) -> str: ...
+def weekheader(width: int) -> str: ...
+def prmonth(theyear: int, themonth: int, w: int = ..., l: int = ...) -> None: ...
+def month(theyear: int, themonth: int, w: int = ..., l: int = ...) -> str: ...
+def calendar(theyear: int, w: int = ..., l: int = ..., c: int = ..., m: int = ...) -> str: ...
+def prcal(theyear: int, w: int = ..., l: int = ..., c: int = ..., m: int = ...) -> None: ...
+
+class HTMLCalendar(Calendar):
+    def formatday(self, day: int, weekday: int) -> str: ...
+    def formatweek(self, theweek: int) -> str: ...
+    def formatweekday(self, day: int) -> str: ...
+    def formatweekheader(self) -> str: ...
+    def formatmonthname(self, theyear: int, themonth: int, withyear: bool = ...) -> str: ...
+    def formatmonth(self, theyear: int, themonth: int, withyear: bool = ...) -> str: ...
+    def formatyear(self, theyear: int, width: int = ...) -> str: ...
+    def formatyearpage(self, theyear: int, width: int = ..., css: Optional[str] = ..., encoding: Optional[str] = ...) -> str: ...
+    if sys.version_info >= (3, 7):
+        cssclasses: List[str]
+        cssclass_noday: str
+        cssclasses_weekday_head: List[str]
+        cssclass_month_head: str
+        cssclass_month: str
+        cssclass_year: str
+        cssclass_year_head: str
+
+if sys.version_info >= (3, 0):
+    class different_locale:
+        def __init__(self, locale: _LocaleType) -> None: ...
+        def __enter__(self) -> _LocaleType: ...
+        def __exit__(self, *args: Any) -> None: ...
+
+else:
+    class TimeEncoding:
+        def __init__(self, locale: _LocaleType) -> None: ...
+        def __enter__(self) -> _LocaleType: ...
+        def __exit__(self, *args: Any) -> None: ...
+
+class LocaleTextCalendar(TextCalendar):
+    def __init__(self, firstweekday: int = ..., locale: Optional[_LocaleType] = ...) -> None: ...
+    def formatweekday(self, day: int, width: int) -> str: ...
+    def formatmonthname(self, theyear: int, themonth: int, width: int, withyear: bool = ...) -> str: ...
+
+class LocaleHTMLCalendar(HTMLCalendar):
+    def __init__(self, firstweekday: int = ..., locale: Optional[_LocaleType] = ...) -> None: ...
+    def formatweekday(self, day: int) -> str: ...
+    def formatmonthname(self, theyear: int, themonth: int, withyear: bool = ...) -> str: ...
+
+c: TextCalendar
+
+def setfirstweekday(firstweekday: int) -> None: ...
+def format(cols: int, colwidth: int = ..., spacing: int = ...) -> str: ...
+def formatstring(cols: int, colwidth: int = ..., spacing: int = ...) -> str: ...
+def timegm(tuple: Union[Tuple[int, ...], struct_time]) -> int: ...
+
+# Data attributes
+day_name: Sequence[str]
+day_abbr: Sequence[str]
+month_name: Sequence[str]
+month_abbr: Sequence[str]
+
+# Below constants are not in docs or __all__, but enough people have used them
+# they are now effectively public.
+
+MONDAY: int
+TUESDAY: int
+WEDNESDAY: int
+THURSDAY: int
+FRIDAY: int
+SATURDAY: int
+SUNDAY: int