JS: Fix extraction of identifiers in EXPORT_BASE context

This is needed to ensure that the base of the RHS of an ImportEqualsDeclaration is bound to a namespace. That is, B below should be bound to a namespace:

import A = B.C.D;

Author: asgerf

javascript/extractor/src/com/semmle/js/extractor/ASTExtractor.java

@@ -747,7 +747,7 @@ public Label visit(MemberExpression nd, Context c) {
         visit(nd.getProperty(), key, 1, IdContext.TYPE_LABEL);
       } else {
         IdContext baseIdContext =
-            c.idcontext == IdContext.EXPORT ? IdContext.EXPORT_BASE : IdContext.VAR_BIND;
+            (c.idcontext == IdContext.EXPORT || c.idcontext == IdContext.EXPORT_BASE) ? IdContext.EXPORT_BASE : IdContext.VAR_BIND;
         visit(nd.getObject(), key, 0, baseIdContext);
         visit(nd.getProperty(), key, 1, nd.isComputed() ? IdContext.VAR_BIND : IdContext.LABEL);
       }

javascript/ql/test/library-tests/TypeScript/RegressionTests/ExportBaseResolution/test.expected

@@ -1 +1,2 @@
+| A | namespace | test.d.ts:1:19:1:19 | A | test.d.ts:10:14:10:14 | A |
 | A | variable | test.d.ts:1:19:1:19 | A | test.d.ts:10:14:10:14 | A |