mergetools: improve configuration for several merge tools
* meld - provide labels for the three panes
* diffmerge - add registry key for detection, improve arguments
* beyond compare - add linux version
* winmerge - improve arguments
* araxis - add configuration, including registry key for detection
* misc - provide default priorities for more tools
adding changeset.txt
adding mymap
0 97e5f848f0936960273bbf75be6388cd0350a32b test