Highlight sp in the Memory segment

[privat]

pc is highlighted in yellow in the Text Segment window and show the current value of pc.

However, in the badly named "Data" Segment window, sp is not shown when the user wants to see the stack and chose current sp.

For the sake of completeness, gp and tp should also be shown, even if we do not present them then in INF2172. pc is also absent in the "Data" Segment window when 0x400000 (.text) is selected.