Always set SSL_COMPRESS_METHOD=NULL with GnuTLS >= 3.6.0
Always set SSL_COMPRESS_METHOD=NULL with GnuTLS >= 3.6.0

Compression support has been removed from GnuTLS with version 3.6.0,
so the gnutls_compression_get() and gnutls_compression_get_name()
functions are deprecated. Always return NULL as the compression
method. The function calls remain for older GnuTLS versions to avoid
reporting the wrong method.

airtower-luna/mod_gnutls,airtower-luna/mod_gnutls,airtower-luna/mod_gnutls