Remove --disable-largefile-fileserver

Remove --disable-largefile-fileserver

Make largefile fileservers the only option. Remove all of the
AFS_LARGEFILE_ENV ifdefs, and tidy up some code as a result of
this change.

Change-Id: I126f7dc5505bbdb28c9337dcd2e81403045707f4
Reviewed-on: http://gerrit.openafs.org/1029
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Andrew Deason <adeason@sinenomine.net>