Fixed randomisers in A1-A4 modes:

- History 4-rolls, history 6-rolls and history 6-rolls 35-bag no longer deal S, Z or O as their first piece
- Added a 7-bag randomiser with the same behaviour (bag7noSZOstart)
- Tweaked the "35-bag" part of the history 6-rolls 35-bag randomiser to work closer to what it's supposed to be
- Switched Marathon AX4's randomiser from history 6-rolls to 7-bag no SZO start

tetris/randomizers/bag7noSZOstart.lua

@@ -0,0 +1,31 @@
+local Randomizer = require 'tetris.randomizers.randomizer'
+
+local Bag7NoSZOStartRandomizer = Randomizer:extend()
+
+function Bag7NoSZOStartRandomizer:shuffleBag()
+    local b = self.bag
+    local ln = #b
+    for i = 1, ln do
+        local j = math.random(i, ln)
+        b[i], b[j] = b[j], b[i]
+    end
+end
+
+local function isnotSZO(x) return not(x == "S" or x == "Z" or x == "O") end 
+
+function Bag7NoSZOStartRandomizer:initialize()
+	self.bag = {"I", "J", "L", "O", "S", "T", "Z"}
+    repeat
+        self:shuffleBag()
+    until isnotSZO(self.bag[7])
+end
+
+function Bag7NoSZOStartRandomizer:generatePiece()
+	if #self.bag == 0 then
+		self.bag = {"I", "J", "L", "O", "S", "T", "Z"}
+        self:shuffleBag()
+	end
+	return table.remove(self.bag)
+end
+
+return Bag7NoSZOStartRandomizer