Reword switch/goto diagnostics "protected scope" diagnostics. Making up a term
"protected scope" is very unhelpful here and actively confuses users. Instead,
simply state the nature of the problem in the diagnostic: we cannot jump from
here to there. The notes explain nicely why not.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@217293 91177308-0d34-0410-b5e6-96231b3b80d8