Wine should warn when ulimit -n needs raising

[Octavian Voicu]

I was looking at http://bugs.winehq.org/show_bug.cgi?id=19861 and it
seemed pretty easy to fix.

In my opinion, the warning should either go in server/file.c -
file_set_error() or in server/fd.c - open_fd().

open_fd() is pretty much the only place where open() is called, so
it's a good candidate.

On the other hand, having the check in file_set_error() might detect
the condition in more instances, but it might also impact performance
(file_set_error() is called really often; having lots of code in one
branch might make the compiler generate slower code).

The warning would go on the ENFILE/EMFILE branches, and maybe also
print the value of getrlimit(RLIMIT_NOFILE) and suggest a fix (editing
/etc/security/limits.conf).

Octavian