Add stubs for HTMLParser, html.parser, and six.moves.html_parser.

stdlib/2.7/markupbase.pyi

@@ -0,0 +1,9 @@
+from typing import Tuple
+
+class ParserBase(object):
+    def __init__(self) -> None: ...
+    def error(self, message: str) -> None: ...
+    def reset(self) -> None: ...
+    def getpos(self) -> Tuple[int, int]: ...
+
+    def unkown_decl(self, data: str) -> None: ...