LRN authored Sep 20, 2018 and Xavier Claessens committed Sep 21, 2018

As we recently established, G_G*_FORMAT macros are for glib
functions *only*. It's not guaranteed that they will work for
C runtime printf() or scanf() variants, and indeed - in this case
they do not (GCC thinks that MSVCRT sscanf() requires %I64 prefix
for 64-bit values; whether that is true or not is irrelevant at this
point - we need to make the werror go away).