* Add CommonCrypto-based crypto utils implementation
Ported and adapted from an old (circa 2014-2015) branch of mine.
DH helpers are based on CCBigNum since CCDH doesn't provide acceptable error
reporting, and SecDH interface is a bit weird and limiting. Given that all
mentioned APIs are private, it doesn't seem to matter which one we're using as
any of them could be changed/removed by Apple at any point.
* Switch Xcode project to CommonCrypto backend
* Update libevent to 2.1.12-stable.
Fixes `kq_init: detected broken kqueue; not using.: Undefined error: 0`
message on start on macOS.
* Do not build libevent samples.
* Explicitly set library type to static on MSVC for libevent.
Co-authored-by: Mitch Livingston <livings124@mac.com>
Co-authored-by: Charles Kerr <charles@charleskerr.com>