I don't know why spl builds on clang but fails on gcc due to a flex
precedence issue. Rather, I don't know why the flex issue doesn't affect
clang. There was a patch provided by a fork nearly four years ago that
fixes the gcc build nicely. The bitbucket issue warns that more eyes
should review the fix though.
Issue 1: roman number II interpreted as I
https://bitbucket.org/kcartmell/marlowe/issue/1/
3f230752a6