Now there's a chance of it actually working, we can add more tests for
the long-broken dict read-and-rewrite cases. This is the first ever
test for the (rarely-used, unpleasant, and until recently completely
broken) ctf_gzwrite function.
libctf/
* testsuite/libctf-regression/gzrewrite*: New test.
* testsuite/libctf-regression/zrewrite*: Likewise.
