[bsp] Add BSP for TM4C1294XL (TI Tiva C Series Connected LaunchPad)

[Kernel] The rt_object_find routine can support to find an object inside a module. The usage is: rt_object_find("module_name/object_name").

pull rt-thread master

[bsp] modify the uart_driver to fit the new rt-thread serial device driver framework. Modify the template.uvproj for auto generate MDK project.

[Drivers] re-write serial framework.

[Kernel] src/timer: fix a compile warning

Next ymodem

[bsp] add the linker script file.

Frequent 'C' on the handshake will confuse some sender(lrzsz for
example).

Make fast path fast and slow path slow.

[bsp] add the lpc43xx bsp support.

2. Fix data transfer size calculate error issue;