[OPENMP] Support for '#pragma omp taskgroup' directive.

Added parsing, sema analysis and codegen for '#pragma omp taskgroup' directive (OpenMP 4.0).
The code for directive is generated the following way:
#pragma omp taskgroup
<body>

void __kmpc_taskgroup(<loc>, thread_id);
<body>
void __kmpc_end_taskgroup(<loc>, thread_id);

llvm-svn: 240011
diff --git a/clang/lib/AST/StmtProfile.cpp b/clang/lib/AST/StmtProfile.cpp
index fb5350e..23f8d0c 100644
--- a/clang/lib/AST/StmtProfile.cpp
+++ b/clang/lib/AST/StmtProfile.cpp
@@ -510,6 +510,10 @@
   VisitOMPExecutableDirective(S);
 }
 
+void StmtProfiler::VisitOMPTaskgroupDirective(const OMPTaskgroupDirective *S) {
+  VisitOMPExecutableDirective(S);
+}
+
 void StmtProfiler::VisitOMPFlushDirective(const OMPFlushDirective *S) {
   VisitOMPExecutableDirective(S);
 }