disallow stack growing in ktap

Set a stack size limit for ktap, if thread exceed the limit,
ktapvm will report "stack overflow".

The default stack size is 120, enlarge this value if script
need more stack.

Make this value to be configurable in future.

Signed-off-by: Jovi Zhangwei <jovi.zhangwei@gmail.com>
add test/stack_overflow.kp

This testcase is purpose for stack overflow checking.

Signed-off-by: Jovi Zhangwei <jovi.zhangwei@gmail.com>