Added Sieve parser code in master

dev/Sieve/Extensions/rfc5183.js

@@ -0,0 +1,38 @@
+/**
+ * https://tools.ietf.org/html/rfc5183
+ */
+
+import {
+	GrammarQuotedString,
+	GrammarStringList,
+	GrammarTest
+} from 'Sieve/Grammar';
+
+export class EnvironmentCommand extends GrammarTest
+{
+	constructor()
+	{
+		super();
+		this.name     = new GrammarQuotedString;
+		this.key_list = new GrammarStringList;
+	}
+
+	get require() { return 'environment'; }
+
+	toString()
+	{
+		return 'environment'
+			+ (this.comparator ? ' :comparator ' + this.comparator : '')
+			+ ' ' + this.match_type
+			+ ' ' + this.name
+			+ ' ' + this.key_list.toString();
+	}
+
+	pushArguments(args)
+	{
+		this.name     = args[args.length-2];
+		this.key_list = args[args.length-1];
+	}
+}
+
+//Sieve.Commands.environment = EnvironmentCommand;