Log Message:
ham/freedv: Patch undefined constant, likely from hamlib

freedv uses FILPATHLEN, which is undefined, and not apparently POSIX.
hamlib defines HAMLIB_FILPATHLEN.  Speculate that hamlib used to not
namespace the constant, that hamlib has been updated, and freedv not,
and patch freedv to match.  freedv is due for an update anyway, and
this can be upstreamed then if it is still an issue.