1. Add interrupt context check function (context_gcc.S)
2. Add lock (semaphore) for IIC, USART and Ethernet drivers to prevent simultaneously access
3. Add multiple channels support for scan mode of ADC driver
4. Modify miscellaneous drivers according to ADC driver changes
5. Add SWO output enable function (board.c)
6. Disable all interrupts in GPIO interrupt handler (hdl_interrupt.c)
7. Add two Ethernet utility functions (drv_ethernet.c)
8. Add accelerometer driver (analog output)
9. Add accelerometer demo (draft, application.c)

git-svn-id: https://rt-thread.googlecode.com/svn/trunk@1654 bbd45198-f89e-11dd-88c7-29a3b14d5316