demandload: implement __call__
demandload can now load functions and classes, and not just modules.
(So if you access foo() rather than just foo.* it still works).
demandload still doesn't work for constants.
#!/bin/sh
mkdir a
cd a
hg init
echo foo > b
hg add b
hg ci -m "b" -d "1000000 0"
chmod -w .hg
cd ..
hg clone a b
chmod +w a/.hg # let test clean up
cd b
hg verify