Log Message:
Update opencpn to 4.6.1. Changes since 4.4.0:
As a successor to OpenCPN version 4.4,  OpenCPN Version 4.6 contains several
new features and enhanced functions. Among them are:
    Substantial functional improvements and performance increases related to
	ENC vector charts.
    User selectable InlandECS mode for increased safety and convenience while
	navigating inland waters.
    Expanded User Manual bundled with Release download.