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 a
cd a
touch empty1
hg add empty1
hg commit -m 'add empty1' -d '1000000 0'
touch empty2
hg add empty2
hg commit -m 'add empty2' -d '1000000 0'
hg up -C 0
touch empty3
hg add empty3
hg commit -m 'add empty3' -d '1000000 0'
hg heads
hg merge 1
# before changeset 05257fd28591, we didn't notice the
# empty file that came from rev 1.
hg status
hg commit -m merge -d '1000000 0'
hg manifest --debug tip