1. Move file, "start_gcc.S", from "libcpu/arm/cortex-m3/" to "bsp/efm32/"
2. Upgrade EFM32 driver libraries (CMSIS and efm32lib) to version 2.2.2
3. Upgrade EFM32 G2xx development kit drivers (EFM32_Gxxx_DK) to version 1.7.2 (from version 1.6.0)
4. Modify the files ("drv_usart.c" and "drv_iic.c") according to the driver libraries upgrading
git-svn-id: https://rt-thread.googlecode.com/svn/trunk@1818 bbd45198-f89e-11dd-88c7-29a3b14d5316