Release 2.0.1

Bug fixes

• resolved issues with Fortran-C interfaces for routines that take
  logical arguments, affecting structure function and QED
  components. Fixed a couple of structure function interface functions
  which had the wrong signature.

• other small fixes for issues picked up with link-time optimization
  (thanks to Alexander Puck Neuwirth for reporting both of the
  above). As a consequence the code can be compiled with LTO by adding
  the following flags.

cmake -DCMAKE_C_FLAGS="-flto" -DCMAKE_CXX_FLAGS="-flto" -DCMAKE_Fortran_FLAGS="-flto"