Fix DESTDIR installs for javadocs

Thanks to Orion Poplawski for noticing the issue
(http://www.open-mpi.org/community/lists/devel/2014/03/14263.php).
Now that we are binding by default, the issue of #slots and what to do when oversubscribed has become a bit more complicated. This isn't a problem in managed environments as we are always provided an accurate assignment for the #slots, or when -host is used to define the allocation since we automatically assume one slot for every time a node is named.

The problem arises when a hostfile is used, and the user provides host names without specifying the slots= paramater. In these cases, we assign slots=1, but automatically allow oversubscription since that number isn't confirmed. We then provide a separate parameter by which the user can direct that we assign the number of slots based on the sensed hardware - e.g., by telling us to set the #slots equal to the #cores on each node. However, this has been set to "off" by default.

In order to make this a little less complex for the user, set the default such that we automatically set #slots equal to #cores (or #hwt's if use_hwthreads_as_cpus has been set) only for those cases where the user provides names in a hostfile but does not provide slot information.

Also cleanup some a couple of issues in the mapping/binding system:

* ensure we only override the binding directive if we are oversubscribed *and* overload is not allowed

* ensure that the MPI procs don't attempt to bind themselves if they are launched by an orted as any binding directive (no matter what it was) would have been serviced by the orted on launch

* minor cleanup to the warning message when oversubscribed and binding was requested

cmr=v1.7.5:reviewer=rhc:subject=update mapping/binding system
osc/sm: do not use gcc specific calls

cmr=v1.7.5:reviewer=jsquyres