RFR: 8296115: Allow for compiling the JDK with strict standards conformance

[Julian Waters]

[JDK-8241499](https://bugs.openjdk.org/browse/JDK-8241499) proposes to set the -permissive- flag for the Microsoft Visual C++ compiler, to enforce strict standards conformance during compilation, making native code behave more strictly. While adding it to default builds is likely not practical given how much testing is required, as an option it can prove helpful in finding areas of native code that are not conformant to the standard. Instead of applying this to just one compiler, we can also include this for every compiler that has support for such a strict mode, which this change does.

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Commit messages:
 - Format
 - Keep docs up to date
 - New --enable-conforming-compilation option

Changes: https://git.openjdk.org/jdk/pull/10912/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=10912&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8296115
  Stats: 43 lines in 5 files changed: 41 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/10912.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10912/head:pull/10912

PR: https://git.openjdk.org/jdk/pull/10912