add libcpu/sim/posix/cpu_port.c
add bsp: simluator for linux
add some comments and clean code in cpu_port.c
re-write the rt_hw_interrupt_enable/disable
add finsh, but still cannot work, only can be built with gcc
surport finsh
add gcc.ld
rewrite cpu_port.c (but still has bug)
fix bug in cpu_port.c(can work very well)
clean code in cpu_port.c, add some comments
recover the terminal's behaviour when runing exit in finsh
use sd as '/' mount ponit
clean code in sd_sim.c to make sure it can be built with gcc in linux
enable FAT and uffs in simlinux/rtconfig.h
fix bug in finsh when built with 64bit-gcc
Merge pull request #18 from prife/finsh-64gcc

fix bug in finsh when built with 64bit-gcc
fix sdl_fb.c to support gcc under linux
enable RTGUI in simlinux
Merge branch 'master' into simposix
merge bsp/simlinux into bsp/simulator