This passes `-Wa,--noexecstack` to the assembler when building
platform-specific assembly files, to signal that a non-executable stack
can be used. This is the same approach as used by Debian
(see https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=430583)
Bumps the OpenSSL version to the latest release, and kills SSL2. (SSL3 was already killed here, so I'm not sure why SSL2 was left around?)
No other changes.