Report each failure mode only once in random-input tests.
Instead of printing each case that fails, print only the first example of each failure mode. This makes it easier to manually check that test has enough coverage. (Programmatic checks for particular coverage could be added.)
For issue 4840 "Merge assertion failure in svn_sort__array_insert"
* subversion/tests/libsvn_subr/mergeinfo-test.c (new_response): New. (test_rangelist_merge_random_canonical_inputs, test_rangelist_merge_random_semi_c_inputs, test_rangelist_merge_random_non_validated_inputs): Use it.