`VERSION_SPECIFIC_LISPDIR' from the command line arguments.
* MU-CFG (PACKAGEDIR): New variable.
- (MU_DIR): Use `VERSION_SPECIFIC_LISPDIR' instead of `LISPDIR'.
(VERSION_SPECIFIC_LISPDIR): New variable.
(TopLevel): Delete code to detect APEL 7.3 or later.
(load-path): Modernize the way of adding the paths of APEL, FLIM,