sslutil: set `_canloaddefaultcerts` to `True` if `ssl.SSLContext` is present
The `load_default_certs()` method was already present when `ssl.SSLContext`
was backported to Python 2.7 (https://hg.python.org/cpython/rev/221a1f9155e2).
== New Features ==
== New Experimental Features ==
== Backwards Compatibility Changes ==
== Internal API Changes ==
* logcmdutil.diffordiffstat() now takes contexts instead of nodes.
* The `mergestate` class along with some related methods and constants have
moved from `mercurial.merge` to a new `mercurial.mergestate` module.