zscanner: add URI and CAA record types support

src/zscanner/scanner.c.g2

src/zscanner/scanner.c.t0

src/zscanner/scanner.rl

src/zscanner/scanner_body.rl

src/zscanner/tests/TESTS

src/zscanner/tests/data/51_URI.in

src/zscanner/tests/data/51_URI.out

src/zscanner/tests/data/52_CAA.in

src/zscanner/tests/data/52_CAA.out

src/zscanner/tests/unittests.in