[Refactoring] Tweak code style
[Refactoring] Slim up code logic
[Refactoring] protectionToChars(PROTKIND kind)
fix bug in protectionToBuffer()
Merge pull request #3906 from 9rnsr/refactor_protection

[Refactoring] around protection code fixed in the PR #3651
Fix Issue 5299 - Protected inheritance is semantically undefined

Deprecation -> Error