Draft: Adding new testcases

Hi,

I have a test case for ov_read_filter in a separate file under test. The test case relies on the existence of an ogg file to use which I believe can be generated from test.c but I have not integrated that part in the test case as I thought it would be best to start a discussion first to see what would be the best way to add such a test case.

This still needs work as you can see but I thought it would be best to get your input on the best way forward to add something like this to the test suite.

Thanks