Backward Compatibility with PFC 5.0

Save files are not compatible between PFC 5.0 and PFC 6.0. The save file system has been revamped so that this should not be the case in any future PFC distributions. Subversion 36 of PFC 5.0 has the to6 command which will export save files in a format consistent with PFC 6.0. Note that FISH functions are not converted and need to be redefined in PFC 6.0. Data files are nearly compatible but there have been a few improvements in syntax. PFC 6.0 includes a built-in file conversion utility that can be accessed with the program convert command.