have been completely distributed across processors,
for gamma point calculations with scalapack.
This implementation save memory and add some communications.
The distribution of becp is performed whenever 
allocate_bec_type is called with a communicator as an additional argument.
add_vuspsi, calbec and s_psi check for the presence of the
communicator within bec type, and if it is present use
a distributed algorithm to compute related quantities.
Exactly the same strategy could be applied to the k-point
and non-collinear case




git-svn-id: http://qeforge.qe-forge.org/svn/q-e/trunk/espresso@8712 c92efa57-630b-4861-b058-cf58834340f0