Reword/rename -Wswitch-unreachable-default.

Rewording the diagnostic to be more precise/correct: "default label in switch
which covers all enumeration values" and changed the switch to
-Wcovered-switch-default

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@148783 91177308-0d34-0410-b5e6-96231b3b80d8
6 files changed