substituted by ringbuf.
CBUF -> RINGBUF rename.

o Moved LICENCE to doc/LICENCE.
o Updated README.adoc
o CBUF -> RINGBUF (arch/arm-cortex-m4/lm4f120/config)
o CBUF -> RINGBUF (arch/avr/atmegaX8/config)
o Added weak symbol to atmegaX8/uart0.c
o CBUF -> RINGBUF (arch/msp430/msp430f21x1/config)
o CBUF -> RINGBUF (arch/sim/sim/config)
o CBUF -> RINGBUF (core/ringbuf.h)
o Added -DNDEBUG as default.
o CBUF -> RINGBUF (test/sim/Makefile)
o util files are now in scripts/util/