Support OpenSSL-0.9.8 with the EXTRA_EXTS feature

OpenSSL-0.9.8 cannot handle an empty extensions section. This change has
the dynamic extensions support place the section reference in the
temporary file at runtime, supporting both 0.9.8 and 1.0.* versions.

Signed-off-by: Josh Cepek <josh.cepek@usa.net>