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.
% build diff with CRLF
adding b
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
% qimport CRLF diff
adding b.diff to series file
applying b.diff
Now at: b.diff