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.
abort: repository a not found!
255
abort: error: Connection refused
255
abort: repository a not found!
255
abort: destination '../a' already exists
255
abort: repository a not found!
255
destination directory: q
abort: destination 'q' already exists