* Added a 'GPIO_EVENTS' table to the database.
* Incremented the database version to 240.
* Implemented GPIO event logging in 'ripcd/local_macros.cpp' and
'ripcd/ripcd.h'.
* Added an 'Events Log' area to RDGpiMon(1) in
'utils/rdgpimon/rdgpimon.cpp' and 'utils/rdgpimon/rdgpimon.h'.
* Added code in rdmaint(1) to purge logged GPIO events in
'utils/rdmaint/rdmaint.cpp' and 'utils/rdmaint/rdmaint.h'.