Rename vfs operation posix_fallocate to just fallocate and add the vfs_fallocate_mode...

Rename vfs operation posix_fallocate to just fallocate and add the vfs_fallocate_mode parameter.

It turns out we need the fallocate operations to be able to both
allocate and extend filesize, and to allocate and not extend
filesize, and posix_fallocate can only do the former. So by defining
the vfs op as posix_fallocate we lose the opportunity to use any
underlying syscalls (like Linux fallocate) that can do the latter
as well.

We don't currently use the non-extending filesize call, but now
I've changed the vfs op definition we can in the future. For the
moment simply map the fallocate op onto posix_fallocate for the
VFS_FALLOCATE_EXTEND_SIZE case and return ENOSYS for the
VFS_FALLOCATE_KEEP_SIZE case.

Jeremy.

Autobuild-User: Jeremy Allison <jra@samba.org>
Autobuild-Date: Sat Dec 18 08:59:27 CET 2010 on sn-devel-104