Fixed minor printf bug.
Stewart Brodie authored
Detail:
  %#x shows a leading 0x (and %#X leads with 0X) only when the value
    to be displayed is NOT zero.
Admin:
  Cross-verified against: C89 standard; C9X standard; gcc 2.95 implementation.
  Built.

Version 5.14. Tagged as 'RISC_OSLib-5_14'
8b52f983