RT3969: Add OPENSSL_SYS_UEFI

This provides support for building in the EDK II reference implementation
of UEFI. Most UEFI firmware in existence uses OpenSSL for implementing
the core cryptographic functionality needed for Secure Boot.

This has always previously been handled with external patches to OpenSSL
but we are now making a concerted effort to eliminate those.

In this mode, we don't actually use the OpenSSL makefiles; we process
the MINFO file generated by 'make files' and incorporate it into the
EDK2 build system.

Since EDK II builds for various targets with varying word size and we
need to have a single prepackaged configuration, we deliberately don't
hard-code the setting of SIXTY_FOUR_BIT vs. THIRTY_TWO_BIT in
opensslconf.h. We bypass that for OPENSSL_SYS_UEFI and allow EDK II
itself to set those, depending on the architecture.

For x86_64, EDK II sets SIXTY_FOUR_BIT and thus uses 'long long' for the
64-bit type, even when building with GCC where 'long' is also 64-bit. We
do this because the Microsoft toolchain has 32-bit 'long'.

Signed-off-by: Rich Salz <rsalz@akamai.com>
Reviewed-by: Tim Hudson <tjh@openssl.org>