RFR: 8317332: Prepare security for permissive-

[Julian Waters]

Prepares java.security.jgss for the permissive- compiler switch by

- Adding scopes so goto doesn't jump over unitialized locals in sspi.cpp
- Adding a static modifier to a mismatched method declaration in NativeCreds.c, as the definition is static

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Commit messages:
 - Prepare security for permissive-

Changes: https://git.openjdk.org/jdk/pull/15996/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=15996&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8317332
  Stats: 183 lines in 2 files changed: 32 ins; 21 del; 130 mod
  Patch: https://git.openjdk.org/jdk/pull/15996.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15996/head:pull/15996

PR: https://git.openjdk.org/jdk/pull/15996