[Windows] Fixing fprintf errors breaking bootstrap?

[Aaron W. LaFramboise]

I am still seeing errors such as this bootstrapping trunk with -Werror. 
  I thought all of this was supposed to be resolved?

../../svn/gcc/bt-load.c: In function 'migrate_btr_defs':
../../svn/gcc/bt-load.c:1415: error: ISO C does not support the 'I64' 
ms_printf length modifier

What needs to be fixed here?  Does HOST_WIDEST_INT_PRINT_DEC need to 
change, or something else?