Add some basic tests for verifying json_object_equal behavior

Do some basic checks on ints, doubles, strings, arrays and "complex" objects.

tests/test_compare.expected

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+JSON integer comparision is correct
+JSON same object comparision is correct
+JSON same integer comparision is correct
+Comparing equal strings is correct
+Comparing different strings is correct
+Comparing equal doubles is correct
+Comparing different doubles is correct
+Comparing equal arrays is correct
+Comparing arrays of different len is correct
+Comparing different arrays is correct
+Comparing different arrays (one empty) is correct
+Comparing JSON object with different key order is correct
+Comparing different objects is correct