setup.py: skip inotify if there's no inotify_add_watch
Debian Etch doesn't include a sys/inotify.h header, which makes it
impossible to compile _inotify.c, making hg uninstallable.
The cc.has_function() method is implemented by trying to compile a
simple C program. Since there's no redirection involved all error
messages are sent to the terminal. This is not particularly pretty
but at least it allows the installation to complete.
#!/bin/sh
hg init
echo "nothing" > a
hg add a
hg commit -m ancestor -d "1000000 0"
echo "something" > a
hg commit -m branch1 -d "1000000 0"
hg co 0
echo "something else" > a
hg commit -m branch2 -d "1000000 0"
hg merge 1
hg id
cat a
hg status