Revert commit by davidm to printf.c that initialized conv_num

Revert commit by davidm to printf.c that initialized conv_num
  needlessly.  To do so increases the generated code size with bcc.
Eliminate duplicate define warnings in wstring.c.
Fix potentially broken preprocessor comparisons.  The preprocessor
  converts integers to maximal signed type, so inequality comparisons
  involving UINTMAX_MAX, ULLONG_MAX, and (if no long long) ULONG_MAX
  were potentially broken.