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
Merge pull request #341 from caitp/cilineendings_unittest

Fix cilineendings_unittest +style issues
Add -Werror=declaration-after-statement to CFLAGS for gcc/clang

Also, use AX_CFLAGS_WARN_ALL (and similarly implement
AX_CFLAGS_WARN_EXTRA) rather than blindly adding these flags
regardless of whether or not they are supported.
Fix 'declaration-after-statement' errors in parser.c