ELPA_development_version_qr: Changes in OpenMP detection
The Intel Fortran compiler accepts the flag "-fopenmp" for compilation with OpenMP. However, the Intel MPI compiler wrapper does not. With the Intel compiler, this leads to the fact, that if ELPA is compiled with the "-fopenmp" flag a not thread-save version of the Intel MPI library is used and the test (with make check) fails. Intel promised to solve this in the future. However, for now the problem is solved in the user friendly way that no manipulation of the MPI compiler wrappers have to be done: For detecting the OpenMP compiler flags, instead of the predefined macro "AC_OPENMP" of autoconf a modified macro "AX_ELPA_OPENMP" is used, which first checks "-openmp" and only then "-fopenmp". Thus it is ensured that the Intel compiler (and mpi compiler wrapper) does not get confused. This is invisible for users calling "configure" during the installation process.