RFR: 8303764: Turn off -Zc:wchar_t- for Visual C++ [v3]

[Julian Waters]

> Was: sunmscapi.dll cannot compile with Visual C++
> 
> `-Zc:wchar_t-` has, until now, been passed to switch off wchar_t as a distinct C++ type when compiling with Visual C++ so jchar and wchar_t are typedef'd to shorts on Windows. After some examination it appears this flag is not actually needed for almost every source file that we have, barring security.cpp, so we could try to remove it and make Windows code behave more like regular C++, since casting between wchar_t and jchar does not appear to happen very often (only appearing in one file!). wchar_t in Standard C is a typedef and is never affected by this flag, and if `-Zc:wchar_t` is enabled for C code, it is simply ignored

Julian Waters has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains four additional commits since the last revision:

 - Merge branch 'openjdk:master' into patch-7
 - -Zc:wchar_t should be enabled
 - Remove explicit wchar_t check in jdk.accessibility
 - sunmscapi.dll cannot compile under permissive-

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/12907/files
  - new: https://git.openjdk.org/jdk/pull/12907/files/e33c9c4d..f5d46e87

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=12907&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=12907&range=01-02

  Stats: 3501 lines in 137 files changed: 2496 ins; 563 del; 442 mod
  Patch: https://git.openjdk.org/jdk/pull/12907.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12907/head:pull/12907

PR: https://git.openjdk.org/jdk/pull/12907