documentation rst sources have moved

[ellie timoney]

Hi,

I've just moved the sphinx-based documentation sources (*.rst etc) from
doc/source/ to a new top-level directory, docsrc/.

Here's the commit:
https://cgit.cyrus.foundation/cyrus-imapd/commit/?id=d14e3d1c494be4efc0fd645e83c47219d9c25819

(The script that rebuilds the cyrusimap.org website has also been
updated to match, and appears to have survived its first run, but let me
know if any problems show up.)

This is part of the work of integrating the sphinx documentation into
the main build system, so that future release distributions contain
current documentation, rather than legacy stuff.  It's the messiest
change, so it got done first.  It means that from now on the doc/ tree
only contains documentation in its final format (whether static or
generated), instead of a mix of final and source versions.  It's a bit
tidier, basically.

If you have documentation work sitting around that hasn't made it
upstream yet, and you need help rebasing your changes onto master, feel
free to drop me a line :)

Cheers,

ellie