Fix Issue #1848: Medley script (and hence loadup script) now checks for lde (ldeinit) on PATH

[fghalasz]

This PR modifies the medley script (and hence the loadup script) to check for and use lde (ldeinit) on PATH.

The following is now how medley script looks for the lde (ldeinit) executable:

1. If the --maikodir argument is given, use the lde in OSVERSION.MACHINETYPE subdir of the value of the argument; if not found ->error
2. If the MAIKODIR env variable is set, use the lde in the OSVERSION.MACHINETYPE subdir of the value of $MAIKODIR; if not found -> error.
3. If neither --maikodir nor MAIKODIR, then look for lde in the following order:
   a. On the PATH
   b. In the OSVERSION.MACHINETYPE subdir of MEDLEYDIR/maiko
   c. In the OSVERSION.MACHINETYPE subdir of MEDLEYDIR/../maiko
   If lde not found in any of these -> error.

[pamoroso]

I tested this PR on Linux Mint 22.1 Cinnamon and my usual apps loadup built successfully. I have nothing unusual to report.

[MattHeffron]

Approved per discussion in meeting 4/28.