Re-organize directory structure (#4971)

See discussion in #2491

Co-authored-by: Ivan Levkivskyi <ilevkivskyi@dropbox.com>

stdlib/sre_compile.pyi

@@ -0,0 +1,31 @@
+import sys
+from sre_constants import (
+    SRE_FLAG_DEBUG as SRE_FLAG_DEBUG,
+    SRE_FLAG_DOTALL as SRE_FLAG_DOTALL,
+    SRE_FLAG_IGNORECASE as SRE_FLAG_IGNORECASE,
+    SRE_FLAG_LOCALE as SRE_FLAG_LOCALE,
+    SRE_FLAG_MULTILINE as SRE_FLAG_MULTILINE,
+    SRE_FLAG_TEMPLATE as SRE_FLAG_TEMPLATE,
+    SRE_FLAG_UNICODE as SRE_FLAG_UNICODE,
+    SRE_FLAG_VERBOSE as SRE_FLAG_VERBOSE,
+    SRE_INFO_CHARSET as SRE_INFO_CHARSET,
+    SRE_INFO_LITERAL as SRE_INFO_LITERAL,
+    SRE_INFO_PREFIX as SRE_INFO_PREFIX,
+)
+from sre_parse import SubPattern
+from typing import Any, List, Pattern, Tuple, Type, Union
+
+if sys.version_info >= (3,):
+    from sre_constants import SRE_FLAG_ASCII as SRE_FLAG_ASCII
+
+MAXCODE: int
+if sys.version_info < (3, 0):
+    STRING_TYPES: Tuple[Type[str], Type[unicode]]
+    _IsStringType = int
+else:
+    from sre_constants import _NamedIntConstant
+    def dis(code: List[_NamedIntConstant]) -> None: ...
+    _IsStringType = bool
+
+def isstring(obj: Any) -> _IsStringType: ...
+def compile(p: Union[str, bytes, SubPattern], flags: int = ...) -> Pattern[Any]: ...