Fix issue 1
Fix issue 1

issue 1: sample/fibo/fibo got segmentation fault with CXXFLAGS='-march=native -O2'
I suppressed inlining of the thread entry point function entry_thread().
Function inlining avoids allocating a new stack frame. That is the cause of the bug.

YutaroOrikasa/user-thread,YutaroOrikasa/user-thread,YutaroOrikasa/user-thread