Improve the diagnostics generated for switch statements missing expressions

- Move the diagnostic to the case statement instead of at the end of the switch
- Add a fix-it hint as to how to fix the compilation error


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@132903 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed