Add an llvm_unreachable to pacify GCC's -Wreturn-type.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@162325 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/StaticAnalyzer/Core/ExprEngineCallAndReturn.cpp b/lib/StaticAnalyzer/Core/ExprEngineCallAndReturn.cpp
index 62e93b1..c96df20 100644
--- a/lib/StaticAnalyzer/Core/ExprEngineCallAndReturn.cpp
+++ b/lib/StaticAnalyzer/Core/ExprEngineCallAndReturn.cpp
@@ -315,6 +315,7 @@
   case NumIPAModes:
     llvm_unreachable("not actually a valid option");
   }
+  llvm_unreachable("bogus IPAMode");
 }
 
 bool ExprEngine::inlineCall(const CallEvent &Call, const Decl *D,