TLS would not be entirely functional without extensions, so unifdef
OPENSSL_NO_TLSEXT.

ok tedu@
ECDH and ECDSA will not work overly well if there is no EC, so unifdef
OPENSSL_NO_EC.

ok tedu@
unifdef -UDOXYGEN and manually remove the few doxygen comments that are not
wrapped in #ifdef DOXYGEN...

Requested by miod@