simulator: fix SDL initialization under Linux

rt_hw_sdl_start should wait untill the rtgui_graphic_set_device is
called int the sdl_loop. Use pthread_cond_wait to achieve this in Linux.
simulator: init SDL after rt_components_init

SDL may use DFS to open files. It should be run after
rt_components_init.
Merge pull request #150 from grissiom/simulator-linux

Simulator linux