Regtests: Remove duplicated test.
BugFix: Avoid conditional jump on uninitialized variable and adjust test tolerance.
DFTB: Reset MPI-RMA regtests.
XC: Make some functionals non-repeatable.
LIBXC: Remove commented out code lines.
Prettify.
OT: Adjust tolerance.
LIBXC: Fix unused-dummy-argument, when LIBXC is not provided.