don't use sizeof(d_name)

its size is undefined according to manpage
don't use GNUmakeisms
set _DEFAULT_SOURCE
expose BSD extensions in server only

and expose them for (Open)Solaris too
don't use sed -i and sed \0

they are not portable
fix start-ssl script
must not use "" inside "" without escaping

the shell might try to execute the unquoted part instead of
concatenating