REORG: include: move openssl-compat.h from common/ to haproxy/

REORG: include: move openssl-compat.h from common/ to haproxy/

This file is to openssl what compat.h is to the libc, so it makes sense
to move it to haproxy/. It could almost be part of api.h but given the
amount of openssl stuff that gets loaded I fear it could increase the
build time.

Note that this file contains lots of inlined functions. But since it
does not depend on anything else in haproxy, it remains safe to keep
all that together.