Under MinGW, when compiling the ecpg test files, you get compiler
warnings about the use of %lld in printf().

These files don't use our printf replacement or the c.h porting layer,
so determine the appropriate format conversion the hard way.
Reviewed-by: Michael Meskes <meskes@postgresql.org>
Discussion: https://www.postgresql.org/message-id/flat/760c9dd1-2d80-c223-3f90-609b615f7918%402ndquadrant.com