Improve support for Typescript declare structures

[christophercurrie]

This change improves support various forms used in Typescript declaration files. It's often necessary to change import resolution to prefer '.d.ts' files over '.js' files, but doing so breaks existing import resolution for certain types of UMD modules (React, for example).

This patch has two improvements:

• It adds support for the export declare function foo() syntax, which wasn't previously recognized
• It adds support for the export = Namespace syntax for exporting everything in a namespace.

The import/named tests were updated to add both variations as additional test files.

[coveralls]

Coverage decreased (-0.09%) to 97.844% when pulling aa290bb on christophercurrie:typescript-declare into 1edbbd0 on benmosher:master.

[coveralls]

Coverage increased (+0.01%) to 97.947% when pulling b52bf3e on christophercurrie:typescript-declare into 1edbbd0 on benmosher:master.

[ljharb]

Seems reasonable.

[christophercurrie]

Thanks. Incorporated your change and fixed the issues with older typescript parsers.

[christophercurrie]

I don’t disagree, but I was trying to follow the style of the file. Happy to make a change, just let me know.

[ljharb]

Thanks, it'd be great to improve the readability in this PR :-) it's not a blocker, tho.

[ljharb]

Thanks, much better :-)

[christophercurrie]

Applied.

[joaovieira]

@christophercurrie this does not cover situations like:

export = supertest;

declare function supertest(app: any): supertest.SuperTest<supertest.Test>;
declare namespace supertest { ... }

and

import { snakeCase } from "./index";
export = snakeCase;

I've raised #1527 for that.

This was already a great help to understand what was going on :)