update typescript, add workaround for microsoft/TypeScript#18276

Author: aeschli

package.json

@@ -20,11 +20,11 @@
     "istanbul": "^0.4.5",
     "mkdirp": "^0.5.1",
     "mocha": "^2.4.5",
-    "typescript": "^2.1.5",
+    "typescript": "^2.5.2",
     "xml2js": "^0.4.16"
   },
   "dependencies": {
-    "vscode-languageserver-types": "^3.3.0-alpha.1",
+    "vscode-languageserver-types": "^3.3.0",
     "vscode-nls": "^2.0.1"
   },
   "scripts": {

src/parser/cssNodes.ts

@@ -429,6 +429,8 @@ export class Stylesheet extends Node {
 }
 
 export class Declarations extends Node {
+	private _declarations: void; // workaround for https://github.com/Microsoft/TypeScript/issues/18276
+
 	constructor(offset: number, length: number) {
 		super(offset, length);
 	}
@@ -1203,6 +1205,8 @@ export class Operator extends Node {
 }
 
 export class HexColorValue extends Node {
+	private _hexColorValue: void; // workaround for https://github.com/Microsoft/TypeScript/issues/18276
+
 	constructor(offset: number, length: number) {
 		super(offset, length);
 	}
@@ -1290,6 +1294,8 @@ export class VariableDeclaration extends AbstractDeclaration {
 }
 
 export class Interpolation extends Node {
+	
+	private _interpolations: void ; // workaround for https://github.com/Microsoft/TypeScript/issues/18276
 
 	constructor(offset: number, length: number) {
 		super(offset, length);