[rhel6-branch] Patches changing the swap size suggestions (#744129)

[Vratislav Podzimek <vpodzime redhat com>]

This is the new version of patches resolving rhbz#744129. Few comments:

1.) As it can be seen on https://bugzilla.redhat.com/show_bug.cgi?id=744129 I haven't been
able to get the info about the upper bound. So I've tested 128 GB swap on x86 architecture
(which should be the most limitting one) and it worked. I think this value should be ok
for users. If somebody wants bigger swap than 128 GB in future, we can modify the constant
after doing some more tests. But I think it's not necessary now.

2.) I know using a constant in storage/formats/swap.py//Swap._maxSize is not ideal, but
the other option was to import storage.formats.swap to iutil.py where this value is
also needed in swapSameAsRam function. Since I think about iutil.py as a set of utility
functions on the lowest level I didn't want to make it dependent on storage.

3.) Should these go also to master and f17-branch?

--
Vratislav Podzimek