RFR: 8247283: Enable the new conformant preprocessor option in Visual Studio [v3]

[Magnus Ihse Bursie]

> The new conformant preprocessor has been feature complete since Visual Studio 2019.
> 
> We should start to use it instead of the traditional preprocessor (which is well known to be non-conforming in various ways). This would bring VS-based usage more in line with other platforms in this area, and remove the need for some workarounds for the traditional preprocessor's behavior. 
> 
> This PR is dependent on [JDK-8293162](https://bugs.openjdk.org/browse/JDK-8293162) "Drop support for VS2017" and [JDK-8293088](https://bugs.openjdk.org/browse/JDK-8293088) "Fix compilation with the new Visual Studio preprocessor".

Magnus Ihse Bursie has updated the pull request incrementally with one additional commit since the last revision:

  Clarify that Visual Studio 16.8 is needed

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/10101/files
  - new: https://git.openjdk.org/jdk/pull/10101/files/b3ccf8fe..6bac1bdc

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=10101&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=10101&range=01-02

  Stats: 8 lines in 3 files changed: 1 ins; 0 del; 7 mod
  Patch: https://git.openjdk.org/jdk/pull/10101.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10101/head:pull/10101

PR: https://git.openjdk.org/jdk/pull/10101