Updated readme file with Botan build info
Updated readme file with Botan build info

Updated readme file to reflect new build information for Botan. To ease
maintenance, Botan is configured as an amalgamation; it means less files
to manage and not having to stick to a specific compiler's ABI as
compared to distributing pre-built library files.

adolby/Kryvos,adolby/Kryvos,adolby/Kryvos