Update prepare_sgxssl.sh

Update OpenSSL package url.

Signed-off-by: Zhang Lili Z <lili.z.zhang@intel.com>

Upate README.md for 2.9 release

Signed-off-by: Li, Xun <xun.li@intel.com>

Linux 2.8 Open Source Gold Release.

Signed-off-by: Zhang Lili Z <lili.z.zhang@intel.com>

Linux 2.7.1 Open Source Gold Release

Updated OpenSSL to 1.1.1d.
Fixed bugs.

Signed-off-by: Li, Xun <xun.li@intel.com>

Update DCAP submodule

Signed-off-by: Zhang Lili Z <lili.z.zhang@intel.com>

Update README.md

Fix ECDSA part in README.md

Signed-off-by: Zhang Lili Z lili.z.zhang@intel.com

Update submodule URL

Signed-off-by: Li, Xun <xun.li@intel.com>

Linux 2.4 Open Source Gold Release

Added support for the Key Separation and Sharing (KSS) feature.
Provided a set of new encryption and decryption functions such as sgx_hmac256_*.
Provided a new untrusted API: sgx_get_target_info.
Provided a new untrusted API: sgx_create_enclave_from_buffer_ex.
Updated the cryptography library and Architecture Enclaves to use Intel(R) Integrated
  Performance Primitives Cryptography 2019 Update 1.
Fixed bugs.

Signed-off-by: Li, Xun <xun.li@intel.com>

Linux 2.3.1 Open Source Gold Release

Bug fixes

Signed-off-by: Li, Xun <xun.li@intel.com>

Merge pull request intel#311 from lzha101/rd_up

Add Ubuntu 16.04 description in README