The PLIST was hardcoded for libtls150.so. Build With tcl 8.5, the
generated library becomes libtls85.so. Use the tcl Makefile.version
file to generate a PLIST_SUBST variable to make this future-proof.
TLS (aka SSL) Channel - can be layered on any bi-directional Tcl_Channel.
Both client and server-side sockets are possible, and this code should work
on any platform as it uses a generic mechanism for layering on SSL and Tcl.