Fix cilineendings_unittest +style issues

Wrapped lines in cilineendings_unittest.cpp to 80 columns
Renamed test file with capital 'I' in filename, so it is lower cased.
Make use of helper functions for error checks where possible
Expect rather than assert where possible
Safety checks to prevent buffer overflows/out of bounds access

Code corrected so that 'self->column' is reset to '1' each time
webvtt_proc_cueline is called