uClibc: fix uClibc implementation of eventfd

uClibc declares eventfd() as taking two arguments but doesn't properly
pass the second argument to the kernel.

The problem is discussed at:
http://lists.uclibc.org/pipermail/uclibc/2012-May/046873.html



This patch is taken from uclibc 0.9.33 git, so will presumably
be integrated in any future releases.

Signed-off-by: Andy Leiserson <andy@leiserson.org>

SVN-Revision: 33478