format. It is targeted at 32 bit microcontrollers, but is also fit for
other embedded systems with tight (2-10 kB ROM, <1 kB RAM) memory
constraints.(http://koti.kapsi.fi/jpa/nanopb/)

How to use the example:
	1. move examples/nanopb to bsp/xxxx/
	2. enable macro RT_USING_NANOPB in rtconfig.h
	3. regenerate the project file (scons --target=xxxx)
	4. rebuild the project

2. [BSP] TM4C129x : According to LunchPad, change device id from TM4C1294XCNZAD   to TM4C1294NCPDT

complete in putc().

SysTick_Config substract one inside the function. So there is no need to
substract one when passing the parameter.

SCons will omit the file in parent dir of SConstruct somehow and build
the object files in that dir instead of in variant dir. This cause
problem because we cannot mix the object files between M0 and M4 which
SCons failed to rebuild. So we have to manually remove the files before
building.

Currently only lpc43xx is supported.

Some compiler is brain-damaged that it will yeild a warning for headers
not ended with a newline. Yes, I mean you, Keil.

M0 core is always booted by the M4 core. It means that if we are running
in M0, the clock is always configured.