The existing platform detection code was derived from the old Beast
library, which was, itself, derived from JUCE.
This commit removes that code and replaces it with the Boost.Predef
library which defines a consistent set of compiler, architecture,
operating system, library, and other version numbers.
For more on Boost.Predef, please see the Boost documentation. The
documentation for the current version as of this writing is at:
https://www.boost.org/doc/libs/1_71_0/doc/html/predef.html
All uses of beast::Thread were previously removed from the code
base, so beast::Thread is removed. One piece of beast::Thread
needed to be preserved: the ability to set the current thread's
name. So there's now a beast::CurrentThreadName that allows the
current thread's name to be set and returned.
Thread naming is also cleaned up a bit. ThreadName.h and .cpp
are removed since beast::CurrentThreadName does a better job.
ThreadEntry is also removed, but its terminateHandler() is
preserved in TerminateHandler.cpp. The revised terminateHandler()
uses beast::CurrentThreadName to recover the name of the running
thread.
Finally, the NO_LOG_UNHANDLED_EXCEPTIONS #define is removed since
it was discovered that the MacOS debugger preserves the stack
of the original throw even if the terminateHandler() rethrows.
