Revert r23043 "Minor code cleanup: Don't print "warning" output in comparison function."

Sigh. It turns out the utest-Split.c relies on the "warning" log level
in order to check for specific code paths. This sucks. The log level
"warning" should please be reserved for things that are actual warnings,
not for code path checks that are used in the unittests.

git-svn-id: svn+ssh://svn.gnucash.org/repo/gnucash/trunk@23048 57a11ea4-9604-0410-9ed3-97b8803252fd