Decreased timeout of forked server.

From "inactive_timeo" (12 m) to "2*interval" (1 m).
Corrected spelling of "identifier".
Eliminated killing of previous process in favor of request reduction.
Eliminated NULLPROC message to test connection.

Added or improved internal documentation. Better placement of
exitIfDone(). Eliminated LDM_CLNT_DONE because it's not used.
Eliminated useless exitIfDone() and unused LDM_CLNT_DONE.

Also improved internal documentation.
Improved copyright notice and internal documentation.
Improved exitIfDone() placement and transfer-mode switching.

Only switch if as_shouldSwitch() is true.
Eliminated redundant and dangerous free_prod_class() before
set_prod_class().
Improved internal documentation.
Documented suicide of duplicate upstream LDM.
v6.11.4.1