Merge branch 'cp/unit-test-reftable-readwrite'

* cp/unit-test-reftable-readwrite: t-reftable-readwrite: add test for known error t-reftable-readwrite: use 'for' in place of infinite 'while' loops t-reftable-readwrite: use free_names() instead of a for loop t: move reftable/readwrite_test.c to the unit testing framework