fixes for use on native Linux and several new command line options
fixes for use on native Linux and several new command line options

thecodemaiden/tinydtls-fork,jvermillard/tinydtls,OlegHahm/tinydtls,thecodemaiden/tinydtls-fork,nmacs/tinydtls,yunus/TinyDTLS-WebID,spark/tinydtls,OlegHahm/tinydtls,OlegHahm/tinydtls,yunus/TinyDTLS-WebID,nmacs/tinydtls,fvdnabee/tinydtls,yunus/TinyDTLS-WebID,thecodemaiden/tinydtls-fork,malvira/tinydtls-code,nmacs/tinydtls,spark/tinydtls,jvermillard/tinydtls,LaKabane/tinydtls,LaKabane/tinydtls,malvira/tinydtls-code,fvdnabee/tinydtls,spark/tinydtls,nmacs/tinydtls,jvermillard/tinydtls,fvdnabee/tinydtls