Define COMP_METHOD when building against LibreSSL

LibreSSL no longer uses compression in ssl.h, so the case that was
formerly activated by defining OPENSSL_NO_COMP is now the default, and
COMP_METHOD isn't defined (it's defined in comp.h, but that's no longer
included by ssl.h). In order to make all the type definitions here line
up with what's actually in LibreSSL's ssl.h, define COMP_METHOD as
void.

This definition is still compatible with the later type declaration in
ssl.py:

  typedef ... COMP_METHOD;
1 file changed