Log Message:
Restore the MASTER_SITE-related changes from the 0.10.4 update
which got reverted in the 0.11.2 update, despite being documented
in the log:

> Due to a change in packaging the docs themes are currently excluded
> from the pypi distribution, breaking the -docs package.  Issue
> ``#761`` should address this upstream; we'll being using GitHub as
> the master site for the time being.

(Also, when touching the base package, make sure the -docs package
still builds.  Makefile.common quite visibly mentions it.)

Bump PKGREVISION, and temporarily invent a DIST_SUBDIR so the
different distfile gets picked up until the next update.