Make debug builds usable without debugging

[Gama11]

Right now, a debug build repeatedly tries to connect to the server when compiled with the hxcpp-debug-server lib and doesn't start until it does. This makes it unusable for anything but debugging, which can be a bit annoying.

One thing we could do is launch the executable with a HXCPP_DEBUGGER environment variable defined, and Server would only be instantiated if that env variable is present. However, that might cause issues when trying to support attach requests (#1).

@nulld Thoughts?

[Gama11]

The Server.connect() loop could maybe also be non-blocking to still allow the application to start? Probably enough to move it to debuggerThreadMain to allow for that. In that case, we might need a stopOnEntry property like the Node debugger has though so you have a way to make sure breakpoints on startup aren't missed.

[nulld]

I thought to limit number of tries will be enough, and start listening on same port for attach request if last try failed.

[Gama11]

Sure, that probably works too.