[jdk8u-dev] RFR: 8221988: add possibility to build with Visual Studio 2019

[Alexey Pavlyutkin]

Hi!

Please review backport of 8221988. This one opens a bunch of backports enabling support of VS2019. The 11u patch applied with the following changes:

- changes to absent documentation files skipped
- resolved baseline conflicts toolchain_windows.m4

Verification: `bash configure` under VS2019 prompt
Regression: `bash configure` under VS2017 prompt

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Commit messages:
 - adding Devkit script
 - 8221988: add possibility to build with Visual Studio 2019

Changes: https://git.openjdk.java.net/jdk8u-dev/pull/33/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk8u-dev&pr=33&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8221988
  Stats: 227 lines in 2 files changed: 223 ins; 0 del; 4 mod
  Patch: https://git.openjdk.java.net/jdk8u-dev/pull/33.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk8u-dev pull/33/head:pull/33

PR: https://git.openjdk.java.net/jdk8u-dev/pull/33