Fixes #283 - make variable 'have_ws' unsigned in 'parse_cueparams'

As mentioned in the issue text, this should never be < 0 (unless
integer overflows, but nevermind that for now)
Merge pull request #283 from caitp/issue-283

[warning] parser.c (lines 881, 884, 887, 890, 893) sign-compare warning