util: Remove various Lua 5.1 compatibility hacks

Part of #1600

util/bitcompat.lua

@@ -5,12 +5,6 @@
 -- Lua 5.2 has it by default
 if _G.bit32 then
 	return _G.bit32;
-else
-	-- Lua 5.1 may have it as a standalone module that can be installed
-	local ok, bitop = pcall(require, "bit32")
-	if ok then
-		return bitop;
-	end
 end
 
 do
@@ -21,12 +15,4 @@ do
 	end
 end
 
-do
-	-- Lastly, try the LuaJIT bitop library
-	local ok, bitop = pcall(require, "bit")
-	if ok then
-		return bitop;
-	end
-end
-
 error "No bit module found. See https://prosody.im/doc/depends#bitop";

util/format.lua

@@ -35,7 +35,6 @@ local control_symbols = {
 	["\030"] = "\226\144\158", ["\031"] = "\226\144\159", ["\127"] = "\226\144\161",
 };
 local supports_p = pcall(string.format, "%p", ""); -- >= Lua 5.4
-local supports_a = pcall(string.format, "%a", 0.0); -- > Lua 5.1
 
 local function format(formatstring, ...)
 	local args = pack(...);
@@ -93,8 +92,6 @@ local function format(formatstring, ...)
 			elseif expects_positive[option] and arg < 0 then
 				args[i] = tostring(arg);
 				return "[%s]";
-			elseif (option == "a" or option == "A") and not supports_a then
-				return "%x";
 			else
 				return -- acceptable number
 			end

util/human/io.lua

@@ -30,10 +30,7 @@ local function getline()
 end
 
 local function getpass()
-	local stty_ret, _, status_code = os.execute("stty -echo 2>/dev/null");
+	local stty_ret = os.execute("stty -echo 2>/dev/null");
-	if status_code then -- COMPAT w/ Lua 5.1
-		stty_ret = status_code;
-	end
 	if stty_ret ~= 0 then
 		io.write("\027[08m"); -- ANSI 'hidden' text attribute
 	end

util/human/units.lua

@@ -6,14 +6,6 @@ local math_max = math.max;
 local math_min = math.min;
 local unpack = table.unpack or unpack; --luacheck: ignore 113
 
-if math_log(10, 10) ~= 1 then
-	-- Lua 5.1 COMPAT
-	local log10 = math.log10;
-	function math_log(n, base)
-		return log10(n) / log10(base);
-	end
-end
-
 local large = {
 	"k", 1000,
 	"M", 1000000,

util/prosodyctl/shell.lua

@@ -80,8 +80,7 @@ local function start(arg) --luacheck: ignore 212/arg
 	if arg[1] then
 		if arg[2] then
 			-- prosodyctl shell module reload foo bar.com --> module:reload("foo", "bar.com")
-			-- COMPAT Lua 5.1 doesn't have the separator argument to string.rep
+			arg[1] = string.format("%s:%s("..string.rep("%q", #arg-2,", ")..")", unpack(arg));
-			arg[1] = string.format("%s:%s("..string.rep("%q, ", #arg-2):sub(1, -3)..")", unpack(arg));
 		end
 
 		client.events.add_handler("connected", function()