add initialization function for OpenMP-related variables
clean up initializations in invert
clean up initializations in hmc_tm
move inclusion of init/init_openmp.h to init/init.h
add OpenMP initialization to gen_sources
add output of requested number of threads at g_debug_level > 0 to init_openmp
Merge pull request #233 from kostrzewa/clean_up_init

Clean up init in main programs