no-unused: don't crash on global augmentation

Fixes: #81

Author: ajafff

rules/noUnusedRule.ts

@@ -259,6 +259,8 @@ function typeParameterMayBeRequired(parameter: ts.TypeParameterDeclaration, usag
             case ts.SyntaxKind.ModuleDeclaration:
                 if ((<ts.ModuleDeclaration>parent).name.kind !== ts.SyntaxKind.Identifier)
                     return ts.isExternalModule(parent.getSourceFile());
+                if (parent.flags & ts.NodeFlags.GlobalAugmentation)
+                    return true;
                 const variable = usage.get(<ts.Identifier>(<ts.ModuleDeclaration>parent).name)!;
                 if (!variable.exported)
                     return variable.inGlobalScope;

test/rules/no-unused/default/type-parameter.ts.lint

@@ -6,3 +6,11 @@ declare module "foo" {
 
 export default class <T> {}
                       ~ [TypeParameter 'T' is unused.]
+
+declare global {
+  namespace jest {
+    interface Matchers<R> {
+      toEqualSomething(argument: string): object;
+    }
+  }
+}