rewrite cpu_port.c (but still has bug)
fix bug in cpu_port.c(can work very well)
Merge branch 'simposix' of github.com:prife/rt-thread into compatibility
add judgement to strcmp(), *s1==0x0.
Now finsh can input sth, and not trigger SIGSEGV.
But! like list() output can trigger SIGSEGV. rt_strlen out of bounds and output's some string is messy code.