patch to add a wrapper around the syscall posix_fadvise

[Filipe David Manana]

Hi,

The following patch adds a new function - file:advise/4
It's a wrapper around the POSIX syscall posix_fadvise, and does nothing
(always returns 'ok') on Windows.

This syscall allows one to declare the access pattern for a file's data.
Useful for many disk IO bound tasks, as it allows the underlying OS to adopt
a better caching strategy for the specified access pattern.

Man page: http://linux.die.net/man/2/posix_fadvise

I assigned the value 31 to the FILE_ADVISE constant because I assigned the
value 30 to a previously submitted patch (which adds a wrapper around the
syscall fdatasync).

Branch posix_fadvise in my github account:

git fetch git://github.com/fdmanana/otp.git posix_fadvise

Documentation and tests are included. Let me know if all is fine.

cheers

-- 
Filipe David Manana,
fdmanana@REDACTED

"Reasonable men adapt themselves to the world.
Unreasonable men adapt the world to themselves.
That's why all progress depends on unreasonable men."