2.7 stub updates (#149)

* Stubgen modules for 2.7

Cookie
email._parseaddr
email.utils
genericpath
linecache
mimetypes
multiprocessing
multiprocessing.process
multiprocessing.util
posixpath
quopri
runpy
weakref
wsgiref.validate

* 2.7/typing.py: add missing __contains__ definition

* 2.7/subprocess.py: make output argument to CalledProcessError optional

Commit f08160bd did the same for py3.

* 2.7/hmac.pyi: add compare_digest

This function was introduced to the 2.7 series in 2.7.7.

* Stubgen 2.7/ssl.pyi

This replaces a nearly-empty handwritten stub.

* Copy constants and other definitions from py3 to py2 ssl.pyi

* 2.7/__future__.pyi: add methods

* 2.7/_weakref.pyi: backport some definitions from 3.x version

* Stubgen 2.7/locale.pyi

Hand-edited to remove declarations that are redundant (and cause
conflicts with) the "from _locale import *" line.

stdlib/2.7/posixpath.pyi

@@ -0,0 +1,50 @@
+# Stubs for posixpath (Python 2)
+#
+# NOTE: This dynamically typed stub was automatically generated by stubgen.
+
+from typing import Any
+from genericpath import *
+
+curdir = ... # type: Any
+pardir = ... # type: Any
+extsep = ... # type: Any
+sep = ... # type: Any
+pathsep = ... # type: Any
+defpath = ... # type: Any
+altsep = ... # type: Any
+devnull = ... # type: Any
+
+def normcase(s): ...
+def isabs(s): ...
+def join(a, *p): ...
+def split(p): ...
+def splitext(p): ...
+def splitdrive(p): ...
+def basename(p): ...
+def dirname(p): ...
+def islink(path): ...
+def lexists(path): ...
+def samefile(f1, f2): ...
+def sameopenfile(fp1, fp2): ...
+def samestat(s1, s2): ...
+def ismount(path): ...
+def walk(top, func, arg): ...
+def expanduser(path): ...
+def expandvars(path): ...
+def normpath(path): ...
+def abspath(path): ...
+def realpath(filename): ...
+
+supports_unicode_filenames = ... # type: Any
+
+def relpath(path, start=...): ...
+
+# Names in __all__ with no definition:
+#   commonprefix
+#   exists
+#   getatime
+#   getctime
+#   getmtime
+#   getsize
+#   isdir
+#   isfile