[v6.x backport] path.win32 related fixes and tests

[TimothyGu]

First commit (#14438):

commit 5180f932eaccfa380f68908b00b098205cb466ba Author: Tobias Nießen <[email protected]> Date: Mon Jul 24 16:20:30 2017 +0200 test: increase coverage for path.parse PR-URL: https://github.com/nodejs/node/pull/14438 Reviewed-By: Refael Ackermann <[email protected]> Reviewed-By: James M Snell <[email protected]> Reviewed-By: Anna Henningsen <[email protected]> Reviewed-By: Luigi Pinca <[email protected]> Reviewed-By: Timothy Gu <[email protected]> Reviewed-By: Colin Ihrig <[email protected]> Reviewed-By: Khaidi Chu <[email protected]> 

Second commit (#14440):

commit 6fa5f3575422a12d374b349e3234331ca5e734c8 Author: Timothy Gu <[email protected]> Date: Mon Jul 24 08:39:02 2017 +0800 path: fix win32 volume-relative paths `path.resolve()` and `path.join()` are left alone in this commit due to the lack of clear semantics. PR-URL: https://github.com/nodejs/node/pull/14440 Fixes: https://github.com/nodejs/node/issues/14405 Reviewed-By: Refael Ackermann <[email protected]> Reviewed-By: Tobias Nießen <[email protected]> 

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• tests and/or benchmarks are included
• commit message follows commit guidelines

Affected core subsystem(s)

path

[TimothyGu]

CI: https://ci.nodejs.org/job/node-test-pull-request/9626/

[tniessen]

Did you intentionally not backport 2ac0aff (part of #14438)?

[TimothyGu]

@tniessen No it was not intentional. I backported the test commit in #14438 because it caused the merge conflict in #14440 but I'll backport the other one too. Thanks for noticing!

[tniessen]

I pushed the missing commit as discussed on IRC.

CI: https://ci.nodejs.org/job/node-test-pull-request/9650/

[MylesBorins]

landed in ee98df8...d75363b