Changed load to check the first line of files for ``FASL FILE'' instead of
assuming that everyone is going to use the same pathname type that we use. Also, when the given filename doesn't exist and doesn't have a type, try ``fasl'' in addition to the machine specific fasl file type. Also added a *load-depth* special that load maintains as the number of times load recurses. The various people who print semicolons at the beginning of the line now print this many semicolons instead of always printing one.