Don't use toupper() in the test program.

We're not including ctype.h in the test program, so don't use toupper().
The test program might not be built with GLib, so don't use
g_ascii_toupper(), either.  Just compare against both 'Y' and 'y'.

Change-Id: Iabc04a5fecb04110c0d16b24a047de72eabbb2bc
Reviewed-on: https://code.wireshark.org/review/4870
Reviewed-by: Guy Harris <guy@alum.mit.edu>