Remove old Fort Mode from frontend Part of ripping out Fort Mode from game schemes. This time for real. - Remove the game modifier button "Fort Mode" - Remove the scheme "Fort Mode" - Remove some fort mode handling code - Keep gfForts symbol to not mess up things too much - Old schemes are still supported, the fortsmode parameter is just ignored

[patterns]
**.h = native
**.c = native
**.cpp = native
**.lua = native
**.txt = native
**.pas = native
**.inc = native
**.hs = native