Define MAXPATHLEN for Hurd-i386 lprng currently FTBFS on hurd-i386, because MAXPATHLEN is not defined for GNU/Hurd. POSIX says it is optional when there is no hard limit. The inlined patch below defines that value to 4096 for GNU. Since lprng does not seen to be the Debian default, cups is, this small patch can be used to make lprng available until all cups tests are OK for Hurd.