console: add cputx for integer types when using newlib
console: add cputx for integer types when using newlib

Too much existing code assumes using msp430-libc or embtextf; implement
the cprintf part of the integer-to-string capability from embtextf.

pabigot/bsp430,pabigot/bsp430,pabigot/bsp430,pabigot/bsp430