RFR: 8242507: Add support for Visual Studio 2019

[Kevin Rushforth]

This PR adds support for Microsoft Visual Studio 2019 (VS 2019), but does not change the default compiler, which
remains at VS 2017 15.9.16. Changing the build compiler to VS 2019 will be proposed in a future PR using a new bug ID,
and isn't planned until after the JDK updates their compiler.

In order to allow developer builds to use Microsoft Visual Studio 2019, we need the following changes at build time and
runtime.

At build time:

1. Copy `vsruntime140_1.dll` (if present) to output `sdk/bin` dir
2. Don't copy the unused  `concrt140.dll` (it is not used in VS 2017 either)

At runtime:

1. Load `vsruntime140_1.dll` if present
2. Don't load the unused `concrt140.dll`

Additionally, I removed two unused build variables, `ext.MSVCR` and `ext.MSVCP`, which would otherwise have needed to
be updated.

I have done a full build and test run using both VS 2017 (which is still the default), and VS 2019.

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Commit messages:
 - 8242507: Add support for Visual Studio 2019

Changes: https://git.openjdk.java.net/jfx/pull/195/files
 Webrev: https://webrevs.openjdk.java.net/jfx/195/webrev.00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8242507
  Stats: 11 lines in 3 files changed: 1 ins; 5 del; 5 mod
  Patch: https://git.openjdk.java.net/jfx/pull/195.diff
  Fetch: git fetch https://git.openjdk.java.net/jfx pull/195/head:pull/195

PR: https://git.openjdk.java.net/jfx/pull/195