Add thread name support

[JackyWoo]

Poco is really a wonderful lib that I use it in my project. Thank you.

I have some questions about Thread.

1. Why current method return 0 when it is main thread, it will cause user confusion
2. Why setName method does not really set thread name.

Expecting your responses

[aleks-f]

1. because main thread is not a Poco::Thread
2. I'm not understanding the question
   

   poco/Foundation/src/Thread.cpp

   Lines 211 to 216 in 191cbdc

   	void Thread::setName(const std::string& name)
   	{
   	FastMutex::ScopedLock lock(_mutex);
   	_name = name;
   	}

[JackyWoo]

@aleks-f thanks for reply.

Why setName method does not really set thread name.

For example use pthread_set_name_np, prctl.

In my case I want get thread name through ps command.

[aleks-f]

That can be added, you can send a pull. However, keep in mind that all ThreadImpls must then have setName implemented (no-op implementations are ok, since we have the _name to fall back to).

Here's a strange way to set it on Windows: https://docs.microsoft.com/en-us/previous-versions/visualstudio/visual-studio-2015/debugger/how-to-set-a-thread-name-in-native-code

[JackyWoo]

ok

[aleks-f]

somewhat related #3384