fpga: Make formspec usage less prone to breakage

mesecons_fpga/init.lua

@@ -203,14 +203,15 @@ plg.from_formspec_fields = function(fields)
 			return nil
 		end
 		local mapping = {
-			[" AND"] = "and",
+			["AND"] = "and",
-			["  OR"] = "or",
+			["OR"] = "or",
-			[" NOT"] = "not",
+			["NOT"] = "not",
-			[" XOR"] = "xor",
+			["XOR"] = "xor",
 			["NAND"] = "nand",
-			["   ="] = "buf",
+			["="] = "buf",
 			["XNOR"] = "xnor",
 		}
+		s = s:gsub("^%s*", "") -- remove leading spaces
 		return mapping[s]
 	end
 	local is = {}