boost: Add upstream patch to fix build on depending projects

boost: Add upstream patch to fix build on depending projects

KDE's krita failed with:
| error: 'typedef void boost::static_visitor<void>::result_type' is inaccessible within this context

Note that only boost 0.173 is affected. 0.172 (dunfell) does not have this
problem and the patch will be included in upcoming 0.174.

Signed-off-by: Andreas Müller <schnitzeltony@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>