workspace - layers are in inverted order after loading saved workspace file

[guano]

When opening a save workspace file, the layers are opened in an inverted order. Those that were in the bottom of the stack will be opened last and will end up in the top of the stack. So any ordering is lost. Must read the list of layers from the last to the first element.

[annakrat]

In 69775:

wxGUI: fix layer order when loading workspace, see #3196

[neteler]

To be backported?

[annakrat]

In 69805:

wxGUI: fix layer order when loading workspace, see #3196 (merge from trunk, r69775)