The term eext=-\sum_i tau_i*Fext_i "energy of external forces" wasn't correct:
a factor "alat" was missing (tau are stored in alat units). Broke minimization
with BFGS under external forces. Printout made consistent with other energy 
terms.


git-svn-id: http://qeforge.qe-forge.org/svn/q-e/trunk/espresso@11200 c92efa57-630b-4861-b058-cf58834340f0