add testftk

NOTE:
this testcase is to demonstrate that how to update ftk ui in
another thread, but ftk will stuck.
fix testftk stuck bug when sending too much event in a short time

NOTE: primary source(pipe) is used both by ftk itself and the main-thread.
when the pipe is full, the main-thread will be blocked, then the
ftk-thread will be blocked when it write to the pipe