Compile errors for VS Code codebase with TS 3.4

[mjbvz]

TypeScript Version: 3.4.0-dev.20190311

Issue
After updating to build VS Code with TS 3.4, I ran into a handful of problems that had to be worked around. Here's the change that added the workarounds.

To repo original issues:

1. In VS Code project
2. git checkout 50ee8c5fa50f5ba85a130975e41a43dc06f554a0~1
3. Build VS Code using 3.4.0-dev.20190311: tsc -p src/tsconfig.json --watch

I have not been able to create more minimal repos yet

[RyanCavanaugh]

I've tracked these all down to root causes