use thread_local for ntoa buf

*** 420,429 ****
--- 420,431 ----
  CCERRWARN=              -xwe
  
  # C standard.  Keep Studio flags until we get rid of lint.
  CSTD_GNU89=     -xc99=%none
  CSTD_GNU99=     -xc99=%all
+ # Made up for cw
+ CSTD_GNU11=     -xc11=%all
  CSTD=           $(CSTD_GNU89)
  C99LMODE=       $(CSTD:-xc99%=-Xc99%)
  
  # In most places, assignments to these macros should be appended with +=
  # (CPPFLAGS.first allows values to be prepended to CPPFLAGS).