[OPENMP5.0]Add basic support for declare variant directive.

Added basic support for declare variant directive and its match clause
with user context selector.

llvm-svn: 371892
diff --git a/clang/lib/Basic/OpenMPKinds.cpp b/clang/lib/Basic/OpenMPKinds.cpp
index 761df3b..4859027 100644
--- a/clang/lib/Basic/OpenMPKinds.cpp
+++ b/clang/lib/Basic/OpenMPKinds.cpp
@@ -606,8 +606,6 @@
       break;
     }
     break;
-  case OMPD_declare_simd:
-    break;
   case OMPD_cancel:
     switch (CKind) {
 #define OPENMP_CANCEL_CLAUSE(Name)                                             \
@@ -849,6 +847,8 @@
   case OMPD_taskwait:
   case OMPD_cancellation_point:
   case OMPD_declare_reduction:
+  case OMPD_declare_simd:
+  case OMPD_declare_variant:
     break;
   }
   return false;
@@ -1078,6 +1078,7 @@
   case OMPD_declare_target:
   case OMPD_end_declare_target:
   case OMPD_requires:
+  case OMPD_declare_variant:
     llvm_unreachable("OpenMP Directive is not allowed");
   case OMPD_unknown:
     llvm_unreachable("Unknown OpenMP directive");