Add support for 64 bit integer printing

[RobTillaart]

Added support for printing unsigned long long and long long

solves issue #1236

Included is a reference implementation (commented out) which is a replica of the print code for long.
The code is 2-3x faster with a slightly larger footprint. The performance is gained by working in "16 bit" chunks. Tested on UNO and discussed "long long" ago here - http://forum.arduino.cc/index.php?topic=143584

(minor) Cleanup trailing spaces

[Ivan-Perez]

Should this be added to the String class, so it also supports 64-bit integers?

[RobTillaart]

@Ivan-Perez
The String Class could be extended with two functions (one given here)

String::String(uint64_t value, unsigned char base)
{
init();
char buf[1 + 8 * sizeof(unsigned long)];
ul64toa(value, buf, base);
*this = buf;
}

The AVR stdlib does not have a ul64toa() so you need something like this

// straightforward implementation
void ui64toa(uint64_t v, char * buf, uint8_t base)
{
  int idx = 0;
  uint64_t w = 0;
  while (v > 0)
  {
    w = v / base;
    buf[idx++] = (v - w * base) + '0';
    v = w;
  }
  buf[idx] = 0;
  // reverse char array
  for (int i = 0, j = idx - 1; i < idx / 2; i++, j--)
  {
    char c = buf[i];
    buf[i] = buf[j];
    buf[j] = c;
  }
}

A similar function for a signed version void i64toa()

[facchinm]

This PR was merged in arduino/ArduinoCore-API@3c3b27e , closing here