bug#18406: O_NOATIME patch

[starlight . 2014q3]

Another argument in favor of adding O_NOATIME
support to a limited set of utilities (just
'grep' IMO) is that recent 'ext4' file system
behavior defaults to a mode where ATIME is
updated only once relative to a given MTIME.

For O_NOATIME to be of use, one must care
enough about ATIME to add 'strictatime' to
the mount options in /etc/fstab.

I find this matters to me only in the context
of code development where seeing what has
been recently viewed or compiled (mainly
by me) is of interest.  It's ok if ATIME
is nuked wholesale on occasion since the
usefulness of the value is short.