WolfSSL & improved Makefile

• uSockets now has experimental support for WolfSSL as an alternative to OpenSSL
• Examples now showcase SSL usage by default
• Improved Makefile; build examples with
  • make to build without SSL, all default settings
  • WITH_OPENSSL=1 make to build with OpenSSL 1.1+ support
  • WITH_WOLFSSL=1 make to build with WolfSSL 2.4.0+ support
  • WITH_LIBUV=1 make to build with Libuv support
  • WITH_ASAN=1 make to build with AddressSanitizer for debugging

or any such combination.