always use custom strnlen implementation
always use custom strnlen implementation

To get rid of the strnlen() warning, the reference to strnlen from
stdlib has been replaced by the fallback function that has been
used when HAVE_STRNLEN is not defined. To avoid naming conflicts,
it has been renamed to dtls_strnlen().

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