Warn about the use of BUF_strdup.
OPENSSL_{malloc,free} -> {malloc,free}
Fix memory leak.

OK from beck@ and miod@
The bell tolls for BUF_strdup - Start the migration to using
intrinsics. This is the easy ones, a few left to check one at
a time.
ok miod@ deraadt@
Rewrite i2d_SSL_SESSION to use the ASN1 primitives, rather than using the
horrific macros from asn1_mac.h.

This is a classic example of using macros to obfuscate code, in an attempt
to reduce the line count. The end result is so ridiculously convoluted that
it is completely unreadable and it takes hours to deconstruct the macros
and figure out what is actually going on behind the scenes.

ok miod@
Expand the tlsext_sigalg macros. The end result is about the same number
of lines and much more readable.

ok miod@
Another compression remnant.
Remove license introduced with the PSK code, which has since been removed.

ok deraadt@