测试STM32F4的DSP库基础数学函数：arm_cos_f32和arm_sin_f32和标准库基础数学函数：cosf和sinf的速度差别，并在LCD屏幕上面显示两者计算所用时间，DS0用于提示程序正在运行。(Test STM32F4's DSP library basic mathematical functions: arm_cos_f32 and arm_sin_f32 and standard library basic mathematical functions: the speed