Driving & safemode fixes (PWR)

In response to http://smf.cataclysmdda.com/index.php?topic=4541.0 .  Looks like vehicle-safemode may have been the culprit, but Web Weaver certainly contributed.  Noe Web Weaver's in player.cpp where it belongs and the option calls go direct, thus providing the sort of realtime-changing that players'll want.

Tested and works.  Feel free to pull when ready.

(I thought the engine-upgrade merited a Help update, too.  #4770 is a good solution too.)