Implement OpenCL event_t as Clang builtin type, including event_t related OpenCL restrictions (OpenCL 1.2 spec 6.9)

llvm-svn: 172973
diff --git a/clang/lib/AST/ExprConstant.cpp b/clang/lib/AST/ExprConstant.cpp
index 9965e12..64fd40b 100644
--- a/clang/lib/AST/ExprConstant.cpp
+++ b/clang/lib/AST/ExprConstant.cpp
@@ -5372,6 +5372,7 @@
   case CK_IntegralComplexCast:
   case CK_IntegralComplexToFloatingComplex:
   case CK_BuiltinFnToFnPtr:
+  case CK_ZeroToOCLEvent:
     llvm_unreachable("invalid cast kind for integral value");
 
   case CK_BitCast:
@@ -5859,6 +5860,7 @@
   case CK_ARCExtendBlockObject:
   case CK_CopyAndAutoreleaseBlockObject:
   case CK_BuiltinFnToFnPtr:
+  case CK_ZeroToOCLEvent:
     llvm_unreachable("invalid cast kind for complex value");
 
   case CK_LValueToRValue: