truncated to a small number of significant digits. This is completely
irrelevant in terms of resuts but stll sufficient to yield very small but
visible discrepancies with respect to other XC implementations. I have
converted to full precision all such constans I have spotted. There might
be more cases like these.
PW tests updated: a number of small changes, fixes and corrections
affecting the numerical results had accumulated.
git-svn-id: http://qeforge.qe-forge.org/svn/q-e/trunk/espresso@13592 c92efa57-630b-4861-b058-cf58834340f0