Introduce M:N threads - Ruby master - Ruby Issue Tracking System

Ruby threads (RT in short) are implemented from old Ruby versions and they have the following features:Can be created with simple notation Thread.new{}Can be switched to another ready Ruby thread by:Time-slice.I/O blocking.Synchronization such as Mutex features.And other blocking reasons.Can be interruptible by:OS-deliver signals (only for the main thread).Thread.